Ski in genral

A ski is a long flat device worn on the feet designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now primarily used for recreational and sporting purposes. Also, a ski may denote a similar device used for other purposes than skiing, e.g., for steering snowmobiles.

Snow skis glide on snow because downward pressure, as well as heat from surface friction, melts the snow directly under the ski. This creates a very thin layer of water directly under the ski upon which the ski glides. This is why if there is freezing rain that freezes to the bottom of the ski perhaps when carrying the ski, the ski, when set down on the snow, won't glide until the ice wears off or is knocked off. Ski wax is used to decrease drag by increasing the water repellent properties of the base.