Iodoform gauze is a type of sterile, absorbent fabric used to pack wounds and facilitate blood clotting and general healing. In most cases it is materially identical to standard medical gauze except that it has been treated with or soaked in iodoform, an antiseptic.
GCWR takes into account GVWR and loaded trailer weight. The GCWR is the maximum weight the vehicle can carry and pull together. The loaded trailer weight plus the GVWR of the vehicle cannot exceed the GCWR as specified by the manufacturer.
So if a truck's GVWR is 10,000 pounds, that's the most the manufacturer and government have certified the truck to possibly weigh with fuel, passengers, and cargo. These classes exist for safety regulation, commercial designation, and registration purposes.