[quest88]

Spot on, but nit: Helps you lose altitude quickly, not slows you down.

[FartyMcFarter]

Whether you lose altitude or speed quicker depends on the plane's attitude. Both/either could be the case.

[quest88]

Uh..yes. But that's not the goal of a slip. You're describing the first flight lesson for every pilot. And it's true, but not relevant for the discussion of a slip. The goal of a slip is to quickly lose altitude without changing airspeed. If you need to quickly slow down, chop and drop and pitch up.