What 'polishing' actually means — and what you are really paying for
Your car's paint is a sandwich: primer, colour coat, and on top a transparent clear coat roughly 40–60 microns thick — half the thickness of a human hair. Almost every visible defect, from swirl marks to light scratches to water etching, lives in that clear coat. Polishing is controlled abrasion: a machine, a pad and a compound remove a few microns until the surface is level and the defects are gone. That is the whole trade; everything else — wash, clay, taping, inspection light — exists to make that abrasion safe and even.
Understand too that clear coat is a finite budget: factory paint tolerates only a handful of proper corrections over a car's life. A good polisher measures thickness before cutting and removes the minimum needed; a bad one grinds at maximum cut every visit until the colour coat strikes through on a door edge. A vendor who mentions paint depth readings unprompted understands the material.