The clean and jerk is an Olympic weight lifting movement where the lifter pulls the the bar from the ground, catches it in a squat, stands up from the squat and thrusts the bar over their head.
The clean is performed by pulling on the bar off the ground with a high velocity, once the bar reaches about chest height, the lifter drops under neath the bar and catches it on his shoulder, and sits in a low squat position. The lifter then pushes up with a high velocity to stand back up, this is the clean. The jerk part of the movement is fairly simple. The lifter dips their hips down how ever far they desire, then they thrust the bar up with a high velocity, kick their legs out in a lunge position, catch and hold the bar at rest above their head.