An 18-wheeler truck, also known as a semi-truck or tractor-trailer, is a large vehicle commonly used for transporting goods over long distances. It consists of a tractor unit, which houses the engine and driver's cab, and a trailer that carries the cargo. The name "18-wheeler" comes from the total number of wheels on the truck, with 10 on the tractor and 8 on the trailer. These trucks are essential for the freight industry, as they can carry heavy loads and travel across various terrains. They are equipped with powerful engines and advanced safety features, making them suitable for long-haul transportation.