What is a slice in tennis?

Slice is used to defend, to change the rhythm of a rally, and to approach the net. On a low bounce it skids, which makes it awkward for players who like the ball at waist height.

Most players hit it with a continental grip and a slightly open face.

Questions

Why does a slice stay low?

Backspin lifts the ball in flight and makes it skid rather than kick after the bounce.