The document discusses different types of actuators used in robotics, including pneumatic, hydraulic, and electric actuators. Pneumatic actuators use compressed air and have advantages of low cost and easy control but lack precision. Hydraulic actuators can apply large forces with high power-to-size ratios but require complex servo control and have risks of leakage and fire. Electric actuators are now most common and include stepper motors for position control and DC motors for applications requiring higher power and torque control. The document compares characteristics of different actuator types for robotic applications.