Robotics Glossary

18650

18650 Battery

The 18650 is a type of rechargeable lithium-ion battery. It is commonly used in portable electronics, such as mobile phones, laptops, flashlights, e-cigarettes (Vape) and in electric vehicles.

Actuator

Actuator

An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system. Actuators are powered by electric motors, hydraulic cylinders, pneumatic cylinders, or even compressed air or hand.

ADC

Analog to Digital Converter

An analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.

Algorithm

Algorithm

An algorithm is a finite sequence of well-defined, computer-implementable instructions, typically to solve a class of problems or to perform a computation. Algorithms are always unambiguous and are used as specifications for performing calculations, data processing, automated reasoning, and other tasks.

Android (Operating System)

Android

Android is a mobile operating system developed by Google. It is based on a modified version of the Linux kernel and other open source software, and is designed primarily for touchscreen mobile devices such as smartphones and tablets.

Android (Robot)

Android

An android is a humanoid robot or synthetic organism designed to look and act like a human, especially one with a body that resembles a human's in appearance or behavior.

anion

anion

An anion is a negatively charged ion. It may be a monatomic ion or a polyatomic ion.

Anode

Anode; an electrode through which the conventional current enters

In electronics, an anode is the electrode of an electrolytic cell or a diode through which the conventional current enters. The anode is the electrode at which oxidation occurs.

APA102

APA102

The APA102 is a smart control LED light source that the control circuit and RGB chip are integrated in a package of 5050 components. It internally includes digital port latch and signal reshaping amplification drive circuit. The control circuit can receive and translate data from the microcontroller. The RGB chip can generate a variety of colors.

arduino

An open-source electronics platform based on easy-to-use hardware and software

Arduino is an open-source electronics platform based on easy-to-use hardware and software. It's intended for anyone making interactive projects.

Battery

Battery

A battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights, smartphones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that when connected to an external circuit will flow and power the circuit. It is the movement of those electrons within the external circuit that allows current to flow.

breadboard

breadboard

A breadboard is a construction base for prototyping of electronics. Originally it was literally a bread board, a polished piece of wood used for slicing bread. In the 1970s the solderless breadboard (a.k.a. plugboard, a terminal array board) became available and nowadays the term "breadboard" is commonly used to refer to these.

Buck Converter

Buck Converter

A buck converter is a DC-to-DC power converter that steps down voltage from its input to its output. It is a type of switched-mode power supply (SMPS) that uses a switching regulator to convert the input voltage to a lower output voltage.

Bundle Adjustment

Bundle Adjustment

Bundle adjustment is a technique used in computer vision to refine the parameters of a camera model and the 3D structure of a scene from a set of 2D-3D point correspondences. It is a nonlinear least squares optimization problem.

CAD

Computer Aided Design

"Computer-aided design (CAD) is the use of computers (or workstations) to aid in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing."

Capacitance

Capacitance

Capacitance is the ability of a body to store an electrical charge. Any object that can be electrically charged exhibits capacitance. A common form of energy storage device is a parallel-plate capacitor. In a parallel plate capacitor, capacitance is directly proportional to the surface area of the conductor plates and inversely proportional to the separation distance between the plates.

Capacitor

Capacitor

A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. The capacitor was originally known as a condenser or condensator.

Cathode

Cathode; an electrode through which the conventional current leaves

In electronics, a cathode is the electrode of an electrolytic cell or a diode through which the conventional current leaves. The cathode is the electrode at which reduction occurs.

cation

cation

A cation is a positively charged ion. It may be a monatomic ion or a polyatomic ion.

Cluster

A connected group of Computers

A computer cluster is a set of loosely or tightly connected computers that work together so that, in many respects, they can be viewed as a single system. Unlike grid computers, computer clusters have each node set to perform the same task, controlled and scheduled by software.

columnar

Columnar Database

A columnar database is a database that stores data in columns rather than rows. This makes it fast for read-heavy operations, such as data analysis and business intelligence.

Conductance

Conductance

The electrical conductance of an electrical conductor is a measure of the ease with which an electric current passes. It is the reciprocal of the electrical resistance. A conductor's conductance is often represented by the symbol G.

Current

Current

An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma).

CVZone

An Open Source Computer Vision Library for Python

CVZone is a computer vision library for Python. It is a computer vision library for Python.

dac

Digital to Analog Converter

A digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a device that converts a digital signal into an analog signal. It is used to convert a digital signal into an analog signal.

DDOS

Distributed Denial of Service

A distributed denial-of-service (DDoS) attack is a malicious attempt to disrupt normal traffic of a targeted server, service or network by overwhelming the target or its surrounding infrastructure with a flood of Internet traffic.

debounce

debouncing

Debouncing is the process of removing the small ripple that forms on the output of a switch when it is pressed and released. The effect, from a data input perspective is that the switch is pressed multiple times. Adding a debounce in software or hardware removes this effect.

DHT11

DHT11

The DHT11 is a basic, ultra low-cost digital temperature and humidity sensor. It uses a capacitive humidity sensor and a thermistor to measure the surrounding air, and spits out a digital signal on the data pin (no analog input pins needed). Its fairly simple to use, but requires careful timing to grab data.

Diode

Diode

A diode is a two-terminal electronic component that conducts primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.

Diode

Diode

A diode is a two-terminal electronic component with asymmetric conductance. It has low (ideally zero) resistance to the current in one direction, and high (ideally infinite) resistance in the other.

DuckDB

DuckDB

DuckDB is an in-process SQL OLAP database management system. It is designed to support analytical query workloads.

eeprom

Electrically Erasable Programmable Read-Only Memory

EEPROM (also written E2PROM and pronounced "e-e-prom", "double-e prom", "e-squared", or simply "e-prom") stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store relatively small amounts of data but allowing individual bytes to be erased and reprogrammed.

Electrode

Electrode

An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). The word was coined by William Whewell at the request of the scientist Michael Faraday from two Greek words: elektron, meaning amber (from which the word electricity is derived), and hodos, a way.

electrolyte

electrolyte

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent.

esp32

A series of low-cost, low-power system on a chip microcontrollers with integrated Wi-Fi and dual-mode Bluetooth

ESP32 is a series of low-cost, low-power system on a chip microcontrollers with integrated Wi-Fi and dual-mode Bluetooth.

esp8266

A series of low-cost, self-contained Wi-Fi microcontrollers with integrated TCP/IP stack

ESP8266 is a series of low-cost, self-contained Wi-Fi microcontrollers with integrated TCP/IP stack.

Farad

A unit of electrical capacitance

The farad (symbol: F) is the SI derived unit of electrical capacitance, the ability of a body to store an electrical charge. It is named after the English physicist Michael Faraday.

Firmware

Sofware embedded/fixed in hardware

Firmware is a type of software that is embedded in a hardware device. It is a type of software that is embedded in a hardware device.

fk

Forward Kinematics

The use of the kinematic equations of a robot to compute the joint parameters from specified values for the position of the end-effector.

FreeCAD

FreeCAD

FreeCAD is a free and open-source general-purpose parametric 3D computer-aided design modeler and a building information modeling software with finite-element-method support. It is a free and open-source general-purpose parametric 3D computer-aided design modeler and a building information modeling software with finite-element-method support.

Gears

Gears & Cogs

A gear or cogwheel is a rotating machine part having cut teeth or, in the case of a cogwheel, inserted teeth (called cogs), which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source.

GPIO

General Purpose Input/Output

General-purpose input/output (GPIO) is a generic pin on an integrated circuit whose behavior, including whether it is an input or output pin, is controllable by the user at run time. The name general-purpose input/output reflects the fact that the pin is not dedicated to a specific function at design time.

gps

Global Positioning System

The Global Positioning System (GPS) is a space-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.

H-Bridge

H-Bridge

An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. These circuits are often used in robotics and other applications to allow DC motors to run forwards or backwards.

Hall effect

Hall effect

Hall effect encoders are sensors that use the Hall effect to detect the angular position of a rotating object. The Hall effect is a phenomenon in which a voltage is created when a magnetic field is exposed to a current carrying conductor. In a Hall effect encoder, a magnet is attached to the rotating object, and a Hall effect sensor is placed near it. As the object rotates, the magnetic field changes and the Hall effect sensor detects these changes. The output of the sensor is then used to measure the angular position of the object.

I2C

i2c (I-squared-C)

I2C, pronounced I-squared-C, is a synchronous, multi-master, multi-slave, packet switched, single-ended, serial computer bus invented by Philips Semiconductor (now NXP Semiconductors). It is commonly used for attaching lower-speed peripheral ICs to processors and microcontrollers in short-distance, intra-board communication.

IDE

Integrated Development Environment

An integrated development environment (IDE) is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of at least a source code editor, build automation tools, and a debugger. Examples of popular IDEs are: Microsoft VS Code, Thonny, PyCharm, Mu, Arduino IDE and Arduino Lab for MicroPython

ik

Inverse Kinematics

The use of the kinematic equations of a robot to compute the position of the end-effector from specified values for the joint parameters.

imu

Inertial Measurement Unit

An inertial measurement unit (IMU) is an electronic device that measures and reports a body's specific force, angular rate, and sometimes the magnetic field surrounding the body, using a combination of accelerometers and gyroscopes, or magnetometers.

Inductance

Inductance

In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in electric current through it induces an electromotive force (voltage) in the conductor. It is called self-inductance to distinguish it from mutual inductance, which is the property of a circuit whereby a change in electric current in one circuit produces an electromotive force in another circuit.

JST

JST Connector

"JST connectors are electrical connectors manufactured to the design standards originally developed by J.S.T. Mfg. Co. (Japan Solderless Terminal). JST manufactures numerous series (families) and pitches (pin-to-pin distance) of connectors."

Level shifter

Level shifter

A level shifter is a circuit that converts a signal from one voltage level to another. It is used to convert a signal from one voltage level to another.

lidar

Light Detection and Ranging

LIDAR is a surveying method that measures distance to a target by illuminating that target with a laser light and measuring the reflected light with a sensor.

llm

Large Language Model

A large language model (LLM) is a statistical language model that is trained on a large corpus of text. It is a statistical language model that is trained on a large corpus of text.

Loop closure

Loop closure

Loop closure is a technique used in simultaneous localization and mapping (SLAM) to determine the relative pose of a robot with respect to a previously visited location. Loop closure is a fundamental problem in SLAM.

Machine Learning

Machine Learning

Machine learning (ML) is the study of computer algorithms that improve automatically through experience. It is seen as a subset of artificial intelligence. Machine learning algorithms build a mathematical model based on sample data, known as "training data", in order to make predictions or decisions without being explicitly programmed to do so.

mah

Milliampere hour

An ampere hour or amp hour (symbol: A⋅h or A h; often simplified as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3,600 coulombs.

MatPlotLib

matplotlib

Matplotlib is a plotting library for the Python programming language and its numerical mathematics extension NumPy. It is a plotting library for the Python programming language and its numerical mathematics extension NumPy.

MEMS

MEMS

MEMS (Micro Electro Mechanical Systems) is the technology of miniaturizing mechanical devices and systems by using microelectronic components. MEMS devices are used in a wide range of applications, including automotive, consumer, industrial, medical, and telecommunications. MEMS devices are also used in a variety of sensors, actuators, and other devices.

Motor

Motor

A motor is a machine that converts other forms of energy into mechanical energy. Most motors operate through the conversion of electrical energy into mechanical energy, but some types of motors convert energy from other sources, such as hydraulic or pneumatic energy.

MQTT

MQTT

MQTT is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios.

NAS

Network Attached Storage

Network-attached storage (NAS) is a file-level (as opposed to block-level storage) computer data storage server connected to a computer network providing data access to a heterogeneous group of clients. NAS is specialized for serving files either by its hardware, software, or configuration.

NeoPixel

NeoPixel

NeoPixel is a brand name for individually addressable RGB LED pixels. The pixels are controlled by a single microcontroller, such as an Arduino or Raspberry Pi. The pixels are arranged in a strip, and the strip is connected to the microcontroller. The microcontroller can then control the color of each pixel.

Neural Network

Neural Network

A neural network is a network or circuit of neurons, or in a modern sense, an artificial neural network, composed of artificial neurons or nodes. Thus a neural network is either a biological neural network, made up of real biological neurons, or an artificial neural network, for solving artificial intelligence (AI) problems."

Numpy

Numpy

NumPy is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, along with a large collection of high-level mathematical functions to operate on these arrays. It is a library for the Python programming language, adding support for large, multi-dimensional arrays and matrices, along with a large collection of high-level mathematical functions to operate on these arrays.

NVMe

Non-Volatile Memory Express

Non-Volatile Memory Express (NVMe) is a logical device interface specification for accessing non-volatile storage media attached via a PCI Express (PCIe) bus. The specification was developed by the NVM Express Workgroup, which consists of more than 90 companies; Amber Huffman of Intel was the working group's chair.

Ohms Law

Ohms Law

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship: I = V/R. Where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. Ohms law is named after Georg Simon Ohm, who was a German physicist and mathematician. He discovered Ohm's law in 1827, and published his results in 1827, in the book "Die galvanische Kette, mathematisch bearbeitet" (The Galvanic Circuit Investigated Mathematically).

OLAP

Online Analytical Processing

Online analytical processing (OLAP) is an approach to answering multi-dimensional analytical (MDA) queries swiftly in computing. OLAP is part of the broader category of business intelligence, which also encompasses relational database, report writing and data mining.

OTA

Over The Air

OTA stands for Over The Air. It is a method of updating the firmware of a device without having to connect it to a computer.

Pandas

Pandas

Pandas is a software library written for the Python programming language for data manipulation and analysis. It is a software library written for the Python programming language for data manipulation and analysis.

Parquet

Parquet File Format

Apache Parquet is a free and open-source column-oriented data storage format of the Apache Hadoop ecosystem. It is designed to bring efficiency compared to row-based files like CSV.

PCA9685

PCA9685 Servo Driver Board

The PCA9685 is a 16-channel, 12-bit PWM controller. It is designed to drive LED loads with up to 25 mA per channel. It can be controlled via I2C.

PID

PID

PID is a control loop feedback mechanism. It is used to control the position of a servo.

PoE

Power over Ethernet

Power over Ethernet (PoE) is a technology that allows network cables to carry electrical power. It is a technology that allows network cables to carry electrical power.

Pose Estimation

Pose Estimation

Pose estimation is the process of determining the position and orientation of an object in a given image. Pose estimation is a fundamental problem in computer vision and robotics. It is used in many applications, such as augmented reality, robotics, and autonomous driving.

Pot

Potentiometer

A potentiometer, or pot, is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. A potentiometer is a passive two-terminal resistor.

PWM

Pulse Width Modulation

Pulse-width modulation (PWM) is a modulation technique used to encode a message into a pulsing signal. The width of each pulse is varied in accordance with the message. The pulse width can be varied between 0% and 100% of the period.

pybricks

pybricks

pybricks is a Python library for LEGO® MINDSTORMS® EV3 and LEGO® BOOST. It is a Python library for LEGO® MINDSTORMS® EV3 and LEGO® BOOST.

radar

Radio Detection and Ranging

Radar is a detection system that uses radio waves to determine the distance (ranging), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

ram

Random Access Memory

Random-access memory (RAM) is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. It is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code.

raspberrypi

A series of small single-board computers developed in the United Kingdom by the Raspberry Pi Ltd

The Raspberry Pi is a series of small single-board computers developed in the United Kingdom by the Raspberry Pi Foundation to promote the teaching of basic computer science in schools and in developing countries.

RDBMS

Relational Database Management System

A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. Most databases in widespread use today are based on this model.

redis

redis

Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker.

Resistance

Resistance

Electrical resistance is a measure of the degree to which an object opposes an electric current through it. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens.

RGB LED Strip

RGB LED Strip

An RGB LED strip is a flexible circuit board populated with RGB LEDs. The LEDs are arranged in a row, and the strip is typically 5 mm wide. The strip is powered by a DC voltage, and the LEDs are controlled by a microcontroller.

Robot

Robot

A robot is a machine, especially one programmable by a computer, capable of carrying out a complex series of actions automatically. Robots can be guided by an external control device or the control may be embedded within.

rom

Read Only Memory

Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. It is a type of non-volatile memory used in computers and other electronic devices.

ros

Robot Operating System

The Robot Operating System (ROS) is a set of software libraries and tools that help you build robot applications.

ros2

Robot Operating System, version 2

ROS 2 is the next generation of ROS, built to support the needs of the robotics community in an era of rapidly evolving hardware and increasing competition.

rtk

Real Time Kinematic

Real-time kinematic (RTK) is a satellite navigation positioning technique that allows the user to achieve centimeter-level accuracy. RTK is a form of differential GPS (DGPS) that uses a base station to provide corrections to a rover receiver.

RTSP

Real Time Streaming Protocol

The Real Time Streaming Protocol (RTSP) is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points.

Rust

Rust Programming Language

Rust is a multi-paradigm programming language focused on safety, especially safe concurrency. It is a multi-paradigm programming language focused on safety, especially safe concurrency.

RViz2

ROS Visualization tool

RViz is a 3D visualization tool for ROS. It is a graphical tool that allows the user to visualize data from a ROS system. It is a tool that is used to visualize data from a ROS system.

Servo

Servo

A servo is a device for controlling the position or the velocity of a mechanism. Servos can be pneumatic, hydraulic or electric. In general, the servo operates on one of two principles: the control of angular position or the control of linear position.

Servo Easing

Servo Easing

Servo easing is a technique used to make a servo move smoothly from one position to another.

slam

Simultaneous Localization and Mapping

Simultaneous localization and mapping (SLAM) is the computational problem of constructing or updating a map of an unknown environment while simultaneously keeping track of an agent's location within it.

SPI

SPI

Serial Peripheral Interface Bus (SPI) is a synchronous serial data protocol used by microcontrollers for communicating with one or more peripheral devices quickly over short distances. It can also be used for communication between two microcontrollers.

SQL

Structured Query Language

SQL (Structured Query Language) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, in which there are relations between different entities/variables of the data.

SSD

Solid State Drive

A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage.

stm32

A series of ARM Cortex-M based microcontroller ICs

The STM32 series of 32-bit Flash microcontrollers based on the ARM® Cortex®-M processor is designed to offer new degrees of freedom to MCU users.

tactile switch

tactile switch

A tactile switch is a switch whose operation is perceptible by touch. A main area of tactile switches, are tact switches. These switches are small in size and are commonly used in PDAs, mobile phones and other consumer electronic devices.

tcrt5000

TCRT5000 Line Following Sensor

The TCRT5000 is a reflective optical sensor that combines an infrared emitter and phototransistor in a single package. It is used to detect the presence of an object by measuring the amount of light reflected from the object.

Torque

Torque

In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force, rotational force or turning effect, depending on the field of study. The concept originated with the studies by Archimedes of the usage of levers.

Transistor

Transistor

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

UART

UART (Universal Asynchronous Receiver/Transmitter)

UART is a hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. UART stands for Universal Asynchronous Receiver/Transmitter.

Ultrasonic

Ultrasonic Distance/Range Finder

"Ultrasonic refers to frequencies above the upper limit of the human hearing range, which is generally taken as 20 kHz. Ultrasonic distance sensors use ultrasonic waves to measure the distance to an object."

Voltage

Voltage

Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential energy between two points per unit electric charge. The voltage between two points is equal to the work done per unit of charge against a static electric field to move the test charge between two points.

ws2812

ws2812

The WS2812 is a smart control LED light source that the control circuit and RGB chip are integrated in a package of 5050 components. It internally includes digital port latch and signal reshaping amplification drive circuit. The control circuit can receive and translate data from the microcontroller. The RGB chip can generate a variety of colors.

X11

X11

X11, also known as the X Window System, is a windowing system for bitmap displays, common on UNIX-like operating systems. It is based on the X Window System protocol, which was developed by the Massachusetts Institute of Technology (MIT) Artificial Intelligence Laboratory (AI Lab) in the 1980s.

X11 Forwarding

X11 Forwarding

X11 forwarding is a feature of SSH protocol version 2 that allows a user to connect to a remote host and have the remote host's X11 server forward its display to the user's own X11 server. This allows the user to run graphical applications on the remote host and have them displayed on the local host.