John, I believe the correct acronyms are GVW (gross vehicle weight), the actual total
weight of the vehicle and everything in it, and GVWR (gross vehicle
weight rating), which is the maximum total
weight of the vehicle and everything in it set by the manufacturer.
Similarly, there is GAW and GAWR (gross
axle weight and gross
axle weight rating) for each
axle, as well as GCW and GCWR (gross combined weight and gross combined weight rating) for the actual and maximum weights of tow vehicle and trailer and everything in both.
UVW (unloaded vehicle weight), also called “dry weight” referring specifically to travel trailers, refers to the as-built weight of a trailer with all fixed equipment and options as it leaves the factory. Sadly, it’s not a requirement for manufacturers to weigh each finished trailer and post that number on a label, but some do.
Published dry weights are typically the base UVW for a model before options. That’s why they are particularly unreliable, because most molded trailers have a very long option list. It’s one of the benefits of the factory direct sales model- the ability to have it the way you want it.
The difference between the GVWR and the UVW is the cargo carrying capacity CCC of the trailer. There is a lot of variation in that number among travel trailers, too. Some (toy haulers especially for obvious reason) have a very generous CCC. On others it can be quite limited, but 500-1000# CCC is pretty typical for smaller travel trailers.
Motor vehicles use the terms “curb weight” and “payload” instead of UVW and CCC. Curb weight includes all vehicle fluids, in contrast to dry weight, which does not.
Ratings do not represent the true maximum capabilities of a vehicle. Of course manufacturers leave some safety margin. Your springs don’t immediately break, for example, if you exceed the GAWR by a hundred pounds. You may find the vehicle doesn’t handle as well, and over time things will wear out faster. Manufacturers take all that into account when setting ratings.
However, manufacturer ratings are generally recognized as legal limits in most motor vehicle laws. In theory you could be cited or even impounded for exceeding a weight rating. Enforcement is rare (except large commercial vehicles), but it’s always a possibility if a vehicle appears grossly overloaded or unsafe to a LEO. It could also result in criminal or civil liability if a post-crash investigation uncovers an overweight condition.
Oops... got a little carried away. Hope some of this is helpful to a newcomer...