Back Rank Mate
The back rank mate is the most common tactical pattern in chess: a rook or queen delivers checkmate on the first rank because the king is trapped behind its own pawns. Despite being well-known, it still decides games at every level, even grandmasters fall victim to back rank threats.
The pattern
King on g8 (or g1), pawns on f7, g7, h7 blocking escape. A rook or queen on the first rank delivers mate, Re8#. The king has no escape squares because its own pawns block f8, g8, h8. This is the most basic checkmate pattern, yet it occurs in thousands of games daily.
Prevention: luft
Luft (German for "air"), creating an escape square for the king by advancing one pawn (h3, h6, g3, g6). Making luft costs one tempo but prevents back rank catastrophes. The question: when to make luft? When your opponent has a rook aimed at your back rank and you have no defender.
Exploiting the back rank
Use the threat of back rank mate to win material. If your opponent's pieces are tied to defending the back rank, they can't do anything else. Overloaded defenders are common: a rook defending the back rank can't also protect a hanging piece.
Training
Solve back rank puzzles. In your games, always ask: "Is my back rank safe?"