What are rotary actuators and how do they differ from other rotary tables?

www.motioncontroltips.com: When we think about actuators, we typically think about linear actuators — devices that move loads in a straight line, driven by a screw, belt, or other mechanical power transmission device. But there also exists a class of actuators that provide rotary motion for positioning a load radially around a fixed axis. While these rotary actuators can be driven by pneumatic, hydraulic, or electromechanical power, we’ll focus here on electromechanical versions.