Then, how does a backspin serve work?
In racquet sports and golf, backspin (also known in racket sports as slice or underspin), is a shot such that the ball rotates backwards (as though rolling back towards the player) after it is hit. This direction of spin imparts an upward force that lifts the ball (see Magnus effect).
In this regard, is Ghost serve allowed in table tennis?
“Ghost serve” is a “tricky serve”, short but loaded with heavy underspin. This serve is the table tennis backspin serve, trademark of Ma Lin. The ball makes 3 to 4 bounces on the opposite side and can bounce back to the net.