Officially you get A, B and C
Class A's are built on a truck, bus, or custom motorhome chassis, and looks sort of bus like, the seating is higher up, and they usually have a big bus like windshield.
Class B's are camper vans of one type or another, and are built entirely within the side walls of a standard van body, though historically some have had fiberglass rear extensions and lifted roofs.
Class B+ is much like a class B, but is typically built on a cut away van or sometimes pickup truck chassis with an often wider rear box, these days typically with one or more slides. B+ and C's are much the same though B+ models don't have a bed area over the cab. There are also C's that have had the over cab bed replaced by entertainment centers, or additional storage, some claim these are really B+ models, some people claim they are C's others say there is no such thing as a B+ and they are all class C's
Class C is also built on cut away van or truck cab and typically have a bed or bed space over the cab.
Super C's are in the same format as a class C, but are built on larger MD and HD commercial truck chassis often without a bed over the cab.
There are also some that are hard to classify in this system such as all wheel drive exploration motorhomes,
Class A is generally built on
Unofficially there is also B+, Super C and now something no one really has a name for that is kind of an A/C cross.