Payload
Payload is the weight a vehicle can carry in its cab and bed or cargo area, calculated as GVWR minus curb weight, and it includes the trailer's tongue weight.
How this site uses it
Payload is the limit most often exceeded by pickup owners towing travel trailers: a 10,000 lb trailer at 13% tongue weight uses 1,300 lb of payload before anyone gets in.
The site shows payload per configuration where the manufacturer publishes it. The towing calculator subtracts passengers, cargo and tongue weight to show remaining payload.
Related: GVWR · Tongue weight · Towing calculator