SkierX - perhaps a little "why" will help your understanding?
Take the ski and look at the tip, waist and tail. The waist to tail is the stiffer part of the ski. Stiff means more hold. As Rusty pointed out -- racers like to use their tails. The stiff tail can hold better on icy, rutted conditions. At the same time, weighting the waist to tail section will give you a faster ride -- yet another reason racers like to use their tails. It's not just for racers, of course, you'll find that more agressive skiers will engage their tails so that they control their turns at faster speeds or on slicker conditions. Some argue it's the "only way to ski"
Conversely -- the tip to waist is the softer and slower part of the ski. Pressuring the shovel (wide tip) will help you make slower turns, which is especially helpful when you want to ski a tight line down a steep slope.
Hope this helps (and makes sense).