There's two kinds of new car prep that a dealer will do.
The first is the PDI, which was explained earlier. The dealer is going to remove the plastics on the inside and outside of the car which were installed for transport, as well as put in required fuses that were left off intentionally by the factory (protect from theft during shipping), install dealer products such as floor mats, stickers, tint, etc, and finally they will do one last visual inspection to check for scratches or blemishes that need to be reported and fixed.
The second prep is when they prep the car for customer delivery. This includes, but is not limited to, wash and wax (my dealership always called it a "detail" but it was just a wash and wax with a vacuum if needed), installation of temp tags, a full tank of gas, and any products you purchased with the car such as fabric sealant, glass-etched anti-theft registration, etc. BTW, most of those things are scams. The fabric sealant is nothing more than you could pick up at the store for less than $30 bucks but they charge $200. High profit, low cost items which help put money in the deal for the dealer.