Unlike full trailers, semi-trailers are trailers with their axles located behind the vehicle's center of gravity (when the vehicle is evenly loaded) and equipped with a coupling device that transmits horizontal or vertical forces to the tractor unit. Generally, full trailers have two axles, while semi-trailers have one. A semi-trailer is a vehicle without its own power source, sharing load with the tractor unit and relying on it for traction.
Simply put, a full trailer is connected to the preceding truck via a hook. A semi-trailer is connected to the tractor unit via a towing pin. Common container trucks are typical semi-trailer trains, with the loaded section at the rear being the semi-trailer.
Their uses also differ. Full trailers are mainly used for short-distance transport within factories, ports, docks, and warehouses, while semi-trailers are primarily used for long-distance cargo transport.
