Different from a full trailer, a semi-trailer is a trailer with its axles placed behind the vehicle's center of gravity (when the vehicle is uniformly loaded) and equipped with a coupling device that can transmit horizontal or vertical forces to the towing vehicle. Generally, a full trailer has two axles and a semi-trailer has one axle. A semi-trailer refers to a vehicle that has no power and is jointly supported by the main vehicle for towing and driving.

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

There are also differences in usage. Full trailers are mainly used for short distance transportation in factories, ports, docks, warehouses, and other areas, while semi trailers are mainly used for long-distance transportation of goods.