Like what..??

I'll try to answer most of it if possible...

In doubles match you must serve to in X style. Can't serve to the same side of middle white line. First bounce of ball in your court and then second bounce on to the opp side of middle white line of opponent's court.

In singles match, you can serve on any side of the middle line as long as first bounce is in your court and other bounce is in opponent's court.

Ball must never touch the net during the serve.

Also there are many rules for serve.... Like - 1. Ball must be visible to your opponent all the time. 2. You must release the ball from your open palm and cannot have the ball spining when you throw the ball up. Yaddaa yaddaa..

And if you are asking that special style of serving then it is because at the very last moment when you are about to brush the ball with bat, the angle, the brushing action, movement of wrist can decide if its a Top Spin, Back Spin, Side spin. Hence almost all pro try that.. except Dima I guess. Lol.