Curb Weight is the weight of car with no driver or passengers, but with a full tank of fuel and all other fluids. Optional equipment is not always included, so most cars and trucks on the road weigh more than the manufacturer's published curb weight.
Gross Weight is the loaded weight, as driven. GVWR (Gross Vehicle Weight Rating) is the maximum GVW at which the vehicle can be safely operated. This figure is usually found on a plate near the door jamb or in the owner's manual.