The 2 Step Backs drill is a great basketball agility exercise for working on vertical change of direction. The more efficient you are with your steps the quicker you will become. As a basketball player you want to be able to train yourself to never waist any movement.
When you watch this drill really focus in on the footwork and body movement. That way when you get in the gym and are doing your basketball training you can execute the drill the correct way and maximize your improvement. You also want to make sure that you are not practicing it the wrong way and developing bad habits, because this will just end up hurting the player in the long run.