As a minor clarification, a slip is when the nose points one way (let's say to the right) while the direction of travel is the other (this would then be to the left), simply described as too little rudder (usually while banking/turning). A skid is the opposite situation where the nose leads the direction of travel ,simply described as too much rudder.

Slips (cross-controlling ... say, left aileron and right rudder) are a good way too reduce speed or steepen descents.

And that is how the SLIP/SKID indicator was born ...

Simply a parenthetical post.