'A' Class : A completely custom motorhome body (including cab) mounted on a chassis supplied by a truck manufacturer. Normally the most expensive motorhomes. A purpose built body with integrated cab provides the maximum spaciousness and usually includes beds which can be left permanently made up such as an over cab 'pull-down' double bed above the front seats.
'C' Class A custom motorhome body mounted on a conventional chassis and cab supplied by a truck manufacturer, usually with a fixed in place bed or storage area over the cab, although this space can sometimes be to claustrophic for Adults as headroom is limited and may be more suitable for children. Also known as C-Class. The manufacturer uses the chassis & cab of the base vehicle and builds a new body onto the back of it, these make up the largest proportion of motorhomes at present although A Class ownership numbers are rising fast. The part of the body extending over the cab is known as the 'over-cab' or 'luton'. An alternative, called a 'low-profile' has a much smaller over-cab space that is used purely for cabinets & storage purposes
Campervan A smaller motorhome with either a fixed roof (high-top) or an elevating roof (pop-top / high-top). Broken down as follows:- High Top The alternative motorhome, which takes the whole of a kombi base vehicle, kits it out with an assortment of necessary fixtures and fittings and then adds standing room via a high roof.
Elevating Roof The elevating (or raised) roof motorhome also uses the equivalent kombi base vehicle to the "high top" and has a similar layout and equipment. The roof can be raised when on site to allow the use of the available standing room and then lowered for travelling and storage.
Demountable / Slide-on A demountable motorhome shell, usually with wind-up or hydraulically operated legs, installed on a ute, truck, or flat-tray. A dual purpose motorhome, a standard 'pick-up' type vehicle with a specially made body that fits onto the pickup bed. These have the advantage that you can 'demount' the body at a campsite and then use the pickup for day trips etc.
5th Wheeler An extension on the front of the motorhome section extends over the tow vehicle, and usually mounts onto a turntable, or "wheel" - hence the name "5th Wheeler"
RV Recreational Vehicles. These are the huge American equivalents to their European cousins. Usually much larger in almost all dimensions. Some have accompanying popout/slideouts (Hydraulically operated sections of the motorhome that expand) which allow for increasing living space when the vehicle is on site / stopped.