A robotic arm is a robot manipulator, usually programmable, with similar functions to a human arm. The links of such a manipulator are connected by joints allowing either rotational motion (such as in an articulated robot) or translational (linear) displacement.^[1][2] The links of the manipulator can be considered to form a kinematic chain. The business end of the kinematic chain of the manipulator is called the end effector and it is analogous to the human hand. The end effector can be designed to perform any desired task such as welding, gripping, spinning etc., depending on the application. For example robot arms in automotive assembly lines perform a variety of tasks such as welding and parts rotation and placement during assembly.
In space the Space Shuttle Remote Manipulator System also known as Canadarm or SSRMS and its successor Canadarm2 are examples of multi degree of freedom robotic arms that have been used to perform a variety of tasks such as inspections of the Space Shuttle using a specially deployed boom with cameras and sensors attached at the end effector and satellite deployment and retrieval manoeuvres from the cargo bay of the Space Shuttle.^[3]
The robot arms can be autonomous or controlled manually and can be used to perform a variety of tasks with great accuracy.
The robotic arm can be fixed or mobile (i.e. wheeled) and can be designed for industrial or home applications.
From: 

http://en.wikipedia.org/wiki/Robotic_arm

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Robotics

Robotics is the science and technology of robots, including their design, manufacture, and application. Robotics requires a working knowledge of electronics, mechanics, and software. A person working in the field is a roboticist. The word robot was introduced by Czech writer Karel Čapek in his play R.U.R. (Rossum's Universal Robots) (1920), while the word robotics was first used in print by Isaac Asimov, in his science fiction short story "Runaround" (1941).
A robot is an electro-mechanical or bio-mechanical device that can perform autonomous or preprogrammed tasks. Robots may be used to perform tasks that are too dangerous or difficult for humans, such as radioactive waste clean-up, or may be used to automate mindless repetitive tasks that should be performed with more precision by a robot than by a human, such as automobile production.

The word robot is used to refer to a wide range of machines, the common feature of which is that they are all capable of movement and can be used to perform physical tasks. Robots take on many different forms, ranging from humanoid, which mimic the human form and way of moving, to industrial, whose appearance is dictated by the function they are to perform. Robots can be grouped generally as mobile robots (eg. autonomous vehicles), manipulator robots (eg. industrial robots) and self reconfigurable robots, which can conform themselves to the task at hand. Robots may be controlled directly by a human, such as remotely-controlled bomb-disposal robots and robotic arms; or may act according to their own decision making ability, provided by artificial intelligence. However, the majority of robots fall in between these extremes, being controlled by pre-programmed computers.

From : http://en.wikipedia.org/wiki/Robot

Robot History

Many ancient mythologies include artificial people, such as the mechanical servants built by the Greek god Hephaestus^[96] (Vulcan to the Romans), the clay golems of Jewish legend and clay giants of Norse legend, and Galatea, the mythical statue of Pygmalion that came to life. In Greek drama, Deus Ex Machina was contrived as a dramatic device that usually involved lowering a deity by wires into the play to solve a seemingly impossible problem.
In the 4th century BC, the Greek mathematician Archytas of Tarentum postulated a mechanical steam-operated bird he called "The Pigeon". Hero of Alexandria (10–70 AD) created numerous user-configurable automated devices, and described machines powered by air pressure, steam and water.^[97] Su Song built a clock tower in China in 1088 featuring mechanical figurines that chimed the hours.^[98]

Al-Jazari's programmable humanoid robots

Al-Jazari (1136–1206), a Muslim inventor during the Artuqid dynasty, designed and constructed a number of automated machines, including kitchen appliances, musical automata powered by water, and the first programmable humanoid robots in 1206.^{[citation needed]} The robots appeared as four musicians on a boat in a lake, entertaining guests at royal drinking parties. His mechanism had a programmable drum machine with pegs (cams) that bumped into little levers that operated percussion instruments. The drummer could be made to play different rhythms and different drum patterns by moving the pegs to different locations.
From : http://en.wikipedia.org/wiki/Robot