Ski mountaineering (SKIMO) is a skiing discipline that involves climbing mountains either on skis or carrying them, depending on the steepness of the ascent, and then descending on skis. There are two major categories of equipment used, free-heel Telemark skis and skis based on Alpine skis, where the heel is free for ascents, but is fixed during descent.
Competitive ski mountaineering is typically a timed racing event that follows an established trail through challenging winter alpine terrain while passing through a series of checkpoints. Racers climb and descend under their own power using backcountry skiing equipment and techniques. More generally, ski mountaineering is an activity that variously combines ski touring, Telemark, backcountry skiing, and mountaineering. Source: Wikipedia
More info about the sport:
NORWAY – http://www.skiforbundet.no/telemark/randonee/
INTERNATIONAL – http://www.ismf-ski.org/