The gross vehicle weight rating is how much your trailer weights fully loaded. This number is the weight of the empty trailer, the dry weight which is the weight of the actual house you build on the trailer plus the belongings weight, your belongings etc you put in it. Appliances, furniture, stuff.
The three weights
The tongue weight is the weight that transfers to your towing vehicle when you hitch it up. Empty weights run from 200 lbs to 500 lbs. Loaded weights run from 500 lbs to 1500 lbs depending on the GVWR
The next three things
Your trailer tires must meet the weight capacity you are loading them with. If you have tandem axles (4 tires) and your trailer GVWR is 12,000 lbs, each tire needs to support 3,000 lbs. A triple axle at 18,000 lbs GVWR needs 6 tires at 3,000 lbs capacity to support the load.