Gross Vehicle Mass (GVM)

Maximum allowable weight of the vehicle and all payload, including passengers, luggage, after market accessories and fuel.
GVM = Kerb Weight + Payload.

Gross Trailer Mass (GTM)

Maximum allowable weight supported by the wheels of the trailer whist attached to the tow vehicle.
GTM = ATM – TBM

Gross Combination Mass (GCM)

Maximum allowable weight for both car and trailer whist connected. 
GCM = GVM + GTM

Note: The trailer’s ball weight Is now supported by the car and becomes part of the car’s weight (GVM).

 Aggregate Trailer Mass (ATM)

This is the tare weight of the trailer plus its maximum payload, including luggage, food and water when unhitched from the vehicle.  
GTM + TBM = ATM 

Tow Ball Mass

Also referred to as tow ball weight, is the weight pushing down on the tow ball by the coupling of the trailer being towed. Maximum tow ball weight is specified by both the vehicle and trailer manufacturer. Typically, it is 10% of the Aggregate Trailer Mass (ATM). 

Kerb Weight

This is the weight of the vehicle with a full capacity of lubricant (oil, coolant etc) and full fuel tank/s.

Note: This does NOT include payload such as; passengers, luggage and after market accessories (roof racks, bullbar etc).

Gross Axle Load Rating (GALR)

Otherwise known as Gross Axle Weight Rating (GAWR) is the maximum distributed weight that may be supported by either the rear or front axles independently as set by the manufacturer and/or an authorised engineer.