Purpose of Exercise: To develop the pectoral muscles, triceps second.
Dips are done with your own body weight or with a dip belt for added weight. Dips can be used to train the chest or triceps depending on how your hands are placed. One of the best reasons for dips is that you can get a very long range of motion with this exercise.
Hold yourself at arms length above the bar with your body weight being supported by your arms. Lower yourself all of the way down as far as you can go. From the bottom position press yourself back up to the starting point, and squeeze your pectoral. The farther you lean forward the more pectoral you will use. Crossing your feet behind you will change your center of gravity and will make you lean forward more.