The back rank mate is a checkmate that occurs when a king is trapped on its back rank (the first or eighth rank) and is checkmated by an enemy rook or queen sliding onto that row.
This mate exploits one of the most common weaknesses in chess: a castled king with all three pawns still on their original squares creates a sealed corridor with no escape square. The attacking heavy piece simply lands on the back rank and delivers checkmate. A typical example: White plays Rook to d8 — the black king, walled in by its own pawns on f7, g7, and h7, has nowhere to go.
In practice, always check whether your king has an escape square — often called a "luft" square — by pushing a pawn to g3 (or g6 for Black) before your opponent can threaten your back rank. This simple precaution removes one of the most frequent checkmate patterns seen at every level of play.