The otherservos tag should only be used for questions which do not fall into the servomotor or rcservo (hobbyservo) tags.
Most servo questions should fall into the subcategories of either industrial servomotor or rcservo (with the synonym hobbyservo). Only questions which do not fall into these two sub-categories should use this tag.
Servos, in Robotics, are almost always motors that include a position sensor and a control circuit. A position demand is sent to the control circuit, which in turn drives the motor to the demanded position and holds that position even when outside forces try to move it.
The motor would normally be a brushed or brushless DC electric motor, but might also be a pneumatic muscle, hydraulic ram, voice coil, etc.
The control circuit might be implemented using a micro controller, a PLC, a decicated motion controller (possibly with an external power amplifier), or bespoke circuit (possibly with an Application Specific IC).