The jump shot is a seldom used shot in pool. It takes considerable talent and lots of practice to perfect it. It can, however get you out of trouble in a game.
As you play a pool game, you make a shot and then you are left with your position for the next one. Depending on your skill and luck, you might have a good shot or you may not.
If there is a ball between the cue ball and your desired object ball, you have a problem. You can either choose another ball to shoot at, you can try a bank shot, or you can try to jump the cue ball over the ball that is in your way.
To jump the cue ball, you have to strike it with the cue stick at about a 45 degree angle. Give it a fairly strong hit in just the correct place, and the cue ball will jump up off the table and fly over the blocking ball.
The trick is to hit the cue ball at just the right angle and with the proper force, so that it travels to the ball you are aiming at and sends it into the pocket. While this is easy to describe, it takes a lot of practice to be able to control the cue ball this well.
Below are a couple of videos on jumping balls. In the first, a slow-motion jump is shown. In the second, the shooter explains about how to do the jump and proceeds to make his object ball.