Luft
Also called Air for the king.
A pawn move that gives a castled king an escape square, guarding against back-rank mates.
Usually h3 (or …h6). f3 or f4 also give the king a square, but they open the diagonal from a7 to g1 towards it, and g3 leaves holes on f3 and h3. Make it when you have a spare moment, before the back rank becomes a problem, not after.
Learn and practise it
- Lesson: Back-rank mate