A small light weight servo motor to acuate small parts. These motors are often used in applications where you need to move something to a specific position. They are often used in RC cars and planes. Here they can controll steering of the car or the flaps of the plane.
These motor can be controlled using PWM signals, you would be able to do this directly with a microcontroller, but it is recommended to use a servo driver to control multiple servos at the same time.