Actuator

An actuator is a type of motor that either pushes, pulls, or rotates.
Linear Actuators.
Linear actuators are actuators that move in a straight line. They can be made to move by electricity, or by pushing water or air very hard. When water (or oil or another liquid) is used, it is called hydraulic, and when air is used, it is called pneumatic. Hydraulic systems are used for moving very heavy things, like in cranes, excavators, or bulldozers.