The sidespin is another kind of shot that can be used both to attack or to defend.
Basically, it is a lateral shot (the ball spins from the right to the left or from the left to the right). This produces a low arc shot, but the ball will make a very big curve in the air. This depends on the amount of spin you've imparted to the ball and from the speed your sidespin has, as well as on the angle you used to hit the ball with your bat.
These are sub-pages of the Sidespin shot page (a child in the hiararchy).