A semi-trailer is a trailer in which the axle is placed behind the center of gravity of the vehicle (when the vehicle is evenly loaded) and equipped with coupling devices that transfer horizontal and vertical forces to the tractor. The semi-trailer is generally a three-axis semi-trailer, and its types are divided into eleven meters warehouse semi-trailer, thirteen meters warehouse railings, low plate semi-trailer and many other types. It is a heavy-duty transport vehicle connected to the semi-locomotive through the traction pin 

 Unlike the full trailer, the semi-trailer is a trailer with an axle placed behind the center of gravity of the vehicle (when the vehicle is evenly loaded) and equipped with a coupling device that can transfer horizontal or vertical forces to the tractor, generally two axles for the full trailer and one shaft for the semi-trailer. Semi-trailer refers to a vehicle that is not powered by itself and jointly carries with the main vehicle a vehicle that is driven by the main vehicle. 

 Simply put, the full trailer is connected to the truck in front with hooks. Semi-trailer is connected with the traction seat of the tractor through the traction pin, the common container transport vehicle is a typical semi-trailer train, and the rear loading part is a semi-trailer.