Servo motors are typically AC synchronous brushless motors with built-in positional feedback. Servo motors are used in closed-loop motion control systems where angular position, speed and torque can be very accurately controlled. The rotor of a servo motor uses permanent magnets and can be infinitely positioned between magnetic poles on the stator by varying the voltage and current between windings.
Servo motors are well suited to precision to applications where accurate control of motor speed, position and/or torque is required.