A robot is a machine designed to execute one or more tasks automatically with speed and precision. There are as many different types of robots as there are tasks for them to perform.
There are many different reasons for using a robot but the central reason for most applications is to eliminate a human operator.
A robot has three essential characteristics:

• Controllers :
  The digital computer (both the hardware and the software) acts as a controller to the robot.
• Actuators :
  An actuator is a component of a machine that is responsible for moving or controlling a mechanism or system
• Sensors :
  Sensors are what allow a robot to gather information about its environment.