Servo motor is a subclass of motors in which there is a sensor inbuilt that can assess the speed and position of the rotation. This enables precise control over the speed, torque and position of the rotating arm. Servo motors, unlike the DC motor, can't rotate freely and are limited to 180 degrees back and forth. In other words, the servo motor is a DC motor with some special arrangements of gears and circuitry to precisely control the rotating arm's linear or angular position. This is achieved by a feedback loop when a sensor (i.e. Hall effect sensor) sends the rotating arm's position to a circuit. This circuit interprets the position and sends a signal to the motor to correct its position. This loop runs till the motor requires no correction and the desired position is reached.