Common Trailer Definitions:

Brake controller - A controller mounted inside your towing vehicle that allows electric trailer brakes to become automatically activated along with the braking of the tow vehicle and can manually be used to activate the trailer brakes.

Breakaway switch - A safety device with the purpose of automatically activating the trailer brakes if the trailer becomes disconnected from the hitch while towing.

Coupler - The trailer A-frame section that attaches to the hitch ball.

Curbside - The side of the trailer equivalent to the passenger side of a vehicle in the United States.

Curb Weight - CW - The weight of the tow vehicle or trailer or both together as it is sitting. Without the load you will be adding.

Gross Axle Weight Rating GAWR - maximum allowable weight that a single axle can safely carry.

Gross Vehicle Weight Rating -GVWR -The total allowable or recommended vehicle weight when the trailer is fully loaded. Fully loaded includes the weight of the trailer, contents, components and accessories plus the tongue weight.

Hitch ratings - Hitches are rated by the manufacturers for the the maximum amount of weight they are engineered to hold. There are six classes of hitches. Class 1 - 1000 to 2500 GTW Class 2 - 3500 GTW Class 2.5 - 4,000 GTW Class 3 - 10,000 WD/6,000 GTW Class 4 - 12,000 WD/8,000 GTW Class 5 - 14,000 WD/10,000 GTW

Payload - The maximum allowable weight of cargo and passengers that the vehicle is designed to carry.

Safety chains - A set of chains, usually permanently mounted to the trailers frame with a set of hooks that are either attached to specific places on the hitch or to the tow vehicles's subframe. The chains should be crossed under the tongue of the trailer and will "catch" the tongue of the trailer and keep it off the roadway in case of accidental separation. They keep the trailer attached to the tow vehicle in case of hitch failure. 

Street side -The side of the trailer equivalent to the driver's side of a vehicle in the United States.