Mountaineering is the sport, hobby or profession of walking, hiking, trekking and climbing up mountains. It is also sometimes known as alpinism, particularly in Europe. While it began as an all-out attempt to reach the highest point of unclimbed mountains, it has branched into specializations addressing different aspects of mountains and may now be said to consist of three aspects: rock-craft, snow-craft and skiing, depending on whether the route chosen is over rock, snow or ice. All require great athletic and technical ability, and experience is also a very important part of the matter.