A sled or sleigh is a vehicle with runners for sliding instead of wheels for rolling. It is used for transport on surfaces with low friction, usually snow or ice. Devices to be pulled across bare ground, such as a travois, are not generally called "sleds", although skids often are.
Sleds are typically smaller and simpler than sleighs, though this is not always the case.
With only gravity as the propelling force, a sled can be used downhill, also as a toy.
Alternatively, it may be pulled by animals, usually horses or dogs. It may also be pushed or pulled by humans (playing children, a parent pulling a child, etc.).
A troika is a vehicle drawn by three horses, usually a sled, but it may also be a wheeled carriage.
The fictional flying sleigh of Santa Claus is pulled by flying reindeer. It involves little sliding, perhaps only during taking-off and landing.
The various categories of sleds include: