A sled, sledge, or sleigh is a land vehicle with a smooth underside or possessing a separate body supported by two or more smooth, relatively narrow, longitudinal runners that travels by sliding across a surface. Most sleds are used on surfaces with low friction, such as snow or ice. In some cases, sleds may be used on mud, grass, or even smooth stones. They may be used to transport passengers, cargo, or both. Shades of meaning differentiating the three terms often reflect regional variations depending on historical uses and prevailing climate.