The plyo chin-up will work explosive strength in your back and biceps. This is an advanced exercise. You should be able to do 10 normal chin-ups before you do this variation.
To perform the plyo chin-up, start by hanging from the chin-up bar with an underhand grip. As you pull yourself up, do so in an explosive manner. Pull your chin over the bar as you let go of the bar. Catch yourself on the way down, and repeat.