A vehicle is a mobile machine that transports passengers or cargo. Most often, vehicles are manufactured, such as bicycles, cars, trucks, buses, motorcycles, trains, ships, boats and aircraft. Vehicles that do not travel on land often are called craft, such as watercraft, sailcraft, aircraft, hovercraft, and spacecraft. Land vehicles are classified broadly by what is used to apply steering and drive forces against the ground: wheeled, tracked, railed or skied.