Gearboxes and gearheads are speed reducers that consist of a set of gears, shafts, and bearings in an enclosed housing. In converting inputs to outputs, they reduce RPM and increase torque.
Electric linear actuators have an output rod that provides linear motion via a motor driven ball screw, lead screw, or ACME screw assembly. The actuator's load is attached to the end of a screw or rod and is often unsupported.