I see alot of people talk about this what is it.

Plyometrics are movements like skipping, pogo-stick jumping, stair bounds, jump roping, etc...that are meant to improve quickness.

Plyometrics deals a with jumping drills with the resistance provided by the athlete's own bodyweight.
We perform them to develop the ability to move your own body in an explosive manner. It involves shocking the neuro-muscular system so that an athlete is able to accelerate more quickly, jump higher, hit harder, run faster, and so on. Basically they help transfer weightlifting production into on-field production.