Sliding down a hill on skis is a popular winter activity. Skiing is an exciting way to experience the thrill of going downhill quickly while enjoying the outdoors. Skiing involves sliding down a hill on two long, narrow pieces of wood or metal called skis, which are attached to the feet with bindings. The skier uses poles to help maintain balance and control speed. Skiing can be done on a variety of terrain, from groomed slopes to backcountry trails.