This workout video gives an exercise for you butt or gluteus muscles to tone and strengthen them. Most weight-bearing leg exercises will work out your gluteus muscles to a degree. The same is true with various gym classes, running, rollerblading and ice skating. You can decide to omit targeted exercises for your gluteus muscles from your regular workouts entirely, but it's good to stretch (particularly if you have a day job which requires sitting on a chair), to strengthen and to tone this muscle group from time-to-time. You will not only look much better and sexier, but your muscles will be stronger.
Check out Popular Fitness for a detailed step-by-step text description of this exercise.