Payload
The total weight of people and cargo a car may carry: the gap between its curb weight and its maximum permitted weight (GVWR).
Payload answers a simple question: once the car itself is accounted for, how many kilograms of passengers, luggage, dogs, and roof boxes may you add? Arithmetically it is the gross vehicle weight rating (GVWR) minus the curb weight. Four adults and holiday luggage add up quickly, and everything bolted on afterward, such as a towbar, roof rack, or accessories, draws from the same budget.
Payload rests on two published figures, so a heavier curb weight leaves less of the allowance unless the manufacturer raises the GVWR. Batteries add mass, so it is worth doing the subtraction for an EV, and for camper conversions or small vans, where the allowance matters most.
Exceeding a weight limit can carry penalties. GOV.UK's van guidance, for example, says a driver can be fined or summoned to court if a van exceeds its maximum permitted axle weight. Rules differ by market, so check yours.
Payload is about carrying weight inside the car; pulling weight behind it is towing capacity, and the two budgets interact through the trailer's noseweight.