A trailer is a vehicle driven by a vehicle without its own power drive. The semi-trailer of light weight and high strength steel is composed of a truck (truck or tractor, forklift) and one or more trailers. Trucks and tracts are the main driving vehicles for motor vehicles.

The motor car festival, which is pulled by the main vehicle, is called Trailer. It is an important type of highway transportation, and automobile train transportation is the most effective and simple means to improve economic benefits. It has the advantages of rapid, maneuverable, flexible, safe and so on, and it can conveniently realize section transportation.

The trailer's total weight is called full trailer itself, usually the whole trailer is also called Trailer. Characterized by its own lack of power, independent load bearing, relying on other vehicle traction vehicle trailer is the design and technical characteristics of its traction by the car to normal use of a non-powered road vehicles, used to carry people or goods; special purposes.

Trailers are divided into trailers and semi trailers according to the connection modes between trailers and traction vehicles. A trailer that is towed by a tractor and bears all its mass; a semitrailer by a tr