Explain how the conservation of energy applies to a skier at the top of a mountain?

At a height, an object has potential energy. As it slips to the ground the potential energy is mostly converted to the Kinetic energy or his speed increases. A very small part of potential energy is lost to friction( As ice hardly has any friction)

I found this amazing explanation physicsclassroom. I was going to write one up myself but I thought this was so good that I had to share it: Downhill skiing is a classic illustration of the relationship between work and energy. The skier begins at an elevated position, thus possessing a large quantity of potential energy (i.e., energy of vertical position). If starting from rest, the mechanical energy of the skier is entirely in the form of potential energy. As the skier begins the descent down the hill, potential energy is lost and kinetic energy (i.e., energy of motion) is gained. As the skier loses height (and thus loses potential energy), she gains speed (and thus gains kinetic energy). Once the skier reaches the bottom of the hill, her height reaches a value of 0 meters, indicating a total depletion of her potential energy. At this point, her speed and kinetic energy have reached a maximum. This energy state is maintained until the skier meets a section of unpacked snow and skids to a stop under the force of friction. The friction force, sometimes known as a dissipative force, does work upon the skier in order to decrease her total mechanical energy. Thus, as the force of friction acts over an increasing distance, the quantity of work increases and the mechanical energy of the skier is gradually dissipated. Ultimately, the skier runs out of energy and comes to a rest position. Work done by an external force (friction) has served to change the total mechanical energy of the skier.