Surface PREPARATION means, making the surface the way you want it to be before SURFACE TREATMENT, and then followed by SURFACE FINISH. For example, you need to have a door made for your cupboard. You get a plank first, and use a planer to smoothen the surface to do further work. This process is called surface preparation i.e., levelling, and other things. Surface treatment will be applying a sandpaper to remove further unevenness, etc. and then apply a base coat of termite-proof material, and then drying it, before applying a primary coat of paint and a secondary coat of paint.
Surface finish means ultilmate "finish"ing of the surface i.e., removing any dust particles from the dried paint, if necessary smoothen it, or give a final coat of polyurethane etc to make it scratch-proof.
Basically all "finishing" process will need a preparation, treatment, and finsl finishing.