Mountaineering is the sport, hobby or profession of walking, hiking, backpacking and climbing mountains. It is also sometimes known as alpinism, particularly in Europe. While it began as attempts to reach the highest point of unclimbed mountains, mountaineering has branched into specializations that address different aspects of the mountain and consists of three areas : rock-craft and skiing, depending on whether the route chosen is over rock, snow or ice. All require experience, athletic ability, and technical knowledge to maintain safety.