You will know a ski's sidecut by its shape. Deep sidecuts revolutionized skiing in the mid-1990s. Most of today's skis have deep sidecuts (with a wide tip and tail, and a narrow waist), which help you turn (as long as you can lay a ski on its edge). If you are still skiing on your straight skis from the 80s, trade them in for new technology!
What is that piece of plastic fastened to that pair of skis the guy at the shop showed you last week? It is one of various measures ski makers take to reduce the amount of vibration in the tips and tails of their skis when in use. This leads to easier energy transference for the skier. And that leads to better skiing. Hurray!