
In short, placing the contact point at the bottom of the ball will cause the cue ball to spin back once it contacts the object ball. The more backspin you require, the lower you should put the point and to determine the rate of spin, you select your power.

If you place the cue contact point at the top of the cue ball then this will cause the cue ball to follow through once it makes contact with the object ball, the harder you hit it the more spin will be generated.

Side spin is the final form, you can use this to change the angle that the cue ball takes when it comes off the cushion. If you were to put right hand side spin on, the ball will hit the cushion and bounce more towards the right than if you hit it in the middle. Another thing that has an effect on the angle the cue ball takes when it comes off the cushion is the speed it is travelling at. The faster it is travelling the straighter the ball will bounce and the slower it travels the more of an angle it will take. Very handy for getting out of tight snookers where it would normally be nearly impossible.