It is a ball nut and screw. Like in the attached picture. The motor
rotates the screw through some gearing and the ball nut rides back and forth on the screw driving the arm in and out. The nut is usually sealed and may have oil or grease in it, and the screw may have a light coating of oil or grease, but the precision needed is very high so I don't think it will have much.
Anyway, you really shouldn't be mucking with that part as routine maintenance
You are better off spending your time converting some more $5 bills into lobsters.