Cross-country skiing (also called Nordic, XC, and x-c skiing) involves skiing across flat or rolling country, and is one of the major winter sports in northern and alpine climes. There are two main styles: classical or diagonal style, which involves keeping the skis parallel and in a track, and skate skiing or skating, which involves using the skis to take long, skating strides in a herringbone pattern. Skate skiing came into fashion among racers in the 1980s. It has long been a Winter Olympic sport.
The skis for cross-country skiing in the classical style are longer and narrower than those used for downhill skiing, while skate skis tend to be shorter than for classical style. Cross-country skis also have camber, so that the middle of the ski bends away from the snow. This is because, in classical style, the skier presses in ski wax in the middle to the snow in order to get grip needed to kick forward.
Cross-country skiing often takes place on specially-groomed trails. How the trails are groomed, or prepared, depends on the style of skiing. In classic or diagonal style skiing, there are two grooves for the skis. In skate skiing, trails tend to be hard-packed and to lack grooves.
Cross-country skiing can take place off-trail, or through back country in deep snow, but often requires wider skis with sturdier bindings. Telemarking is a special, graceful style of skiing involving descending long slopes (essentially, downhill skiing) using cross-country skis, making long turns.
Cross-country skiing originated in Scandinavia (thus its alternate name "Nordic" skiing) and was used for winter travel and hunting. Out of this original use has come an unusual sport, combining cross-country skiing and shooting, called the biathlon.