I am not clear on the difference.
Seems there are two sorts- First is a van, like a delivery van that is steel and it then has windows and kit in it. Then there is often the same cab part but with a much bigger back fitted on. Like it has backed into a caravan.
First type seem to be stronger as they have a strong shell and they are nowhere near as wide. Second type seem to have lots of room and perhaps a lower floor plus space over the cab.
I quite fancy converting a van but then I also think that the ready made ones seem to hold their price well and you could buy one for £20 k, use it for a year and then sell it for about what you paid.
Smallest is a campervan, typically built using something like a VW T5. They're just about small enough to use as an everyday vehicle being about the same size as some people carriers. They rarely have a shower on board.
Next size up is also a camper van but known as a panel van conversion. They usually do have a loo and shower on board but it makes them too high to use as everyday vehicles.
Next is a coach built motorhome. Often about the same length and height as a panel van conversion but much more conspicuous. Because they have straight sides, they make more efficient use of the space inside and modern ones usually have all home comforts.
Some motorhomes are known as A Class motorhomes (don't know why). Instead of using the cab from the donor vehicle, they're totally "coachbuilt" and makes them feel very spacious inside.
American RV's are big, both inside and outside. Very thirsty engines and a bit impractical on uk and european roads. They're often too big for most pitches on european campsites. In the US and Canada though they work very well.
Strangely, in terms of cost, small campervans, panel van conversions and coach built motorhomes cost about the same when new. How you assess their value though is up to you. Campers and panel vans are usually fairly unobtrusive and perhaps more practical; motorhomes are a bit gaudy I suppose, can attract attention, but are probably easier to live in as they have more space. Yer pays yer money etc.