Skiing involves sliding across snow while wearing boots with skis affixed. Skis are typically long and narrow, constructed of wood, plastic, or metal. Skiers commonly use ski poles to aid in balance and forward motion. Skiing can be divided into three types: cross-country, freestyle, and downhill, each needing a distinct set of skills and equipment. Skiing is both a popular recreational activity and a competitive sport, and there are numerous ski resorts around the globe that offer amenities and services to skiers of all abilities.