what is difference between servos & servo motors?
In common usage, the term “servo” is an abbreviation of “servo motor”, particularly when referring to the low-cost lightweight servo motors originally used in radio control models ("RC servos"), which have de-facto-standard control signals and sizes.

More formally, “servo” is an abbreviation of “servomechanism”, which is a control system that uses negative feedback to steer the system to the target accurately. A servomechanism involving a motor does not necessarily seek a target position; for example a cruise control or governor controls speed. Servomechanisms can also control non-mechanical states.



A servo motor is not a distinct type of motor in the way “induction”, “brushless” and such are; you can turn any motor into a servo motor by adding a sensor to detect its position or speed, and connecting this combination to a controller. The controller may or may not be considered part of the "servo motor" itself; in particular, in industrial controls the controller is likely to be a separate unit.



In most cases, if you see the word “servo” and you're not reading about control systems, it will be referring to a servo motor, but it may occasionally refer to a different control system; use context to determine whether it makes sense that there's a motor involved.