In this video we show the steps taken in an in-store optical lab to 'grind' a lens for a pair of eyeglasses.
In an optical store, the process is to
center and align a lens that matches the prescribed power, and shape it to fit the frame in the right place.
Putting the power on the lens is done at a 'surfacing' laboratory, where optical stores order their lens blanks from.
Hopefully this takes some of the mystery out of what happens where all that noise is going on in the back of the optical shop.