If you imagine it like this, a girl going out for the night puts on makeup and looks great, after she comes home she washes her face and looks the same as she did before putting on makeup. That is a valet, we are in essence applying makeup (products containing fillers) to the paint to hide the scratches and swirls and produce a shine. These will gradually fade/wash off over time usually a couple of months and you will be back to square one.
A detail is like a girl going for cosmetic surgery and getting a chemical peel where the surgeon removes a layer of skin exposing a fresh layer and she looks great for a longer period of time. The detailer machine polishes the paint removing a microscopic layer so the swirls, scratches, oxidization and marring are removed.