Robin2:
I wonder if there is some serious confusion here seeing as the OP is a beginner.For Arduino projects the word "servo" usually means the sort of thing that is used to move the control surfaces of model aircraft. It's often referred to as a hobby servo or an R/C servo - but mostly just as a "servo".
True enough. My background led me to answer as I did. The first servo I worked on was actually hydraulic; a head positioner on a 10 megabyte disk drive, then a large variety of electrical ones after that.