Back-rank mate is one of the most common mating patterns in chess and claims victims at every level of play. It occurs when a player's king is stuck on the back rank behind unmoved pawns (typically on g7, f7, h7 for Black or g2, f2, h2 for White), and a rook or queen invades the back rank to deliver checkmate.
Preventing back-rank mate is straightforward: create a "luft" (breathing room) by advancing one of the pawns in front of the king, typically h3 or g3 (h6 or g6 for Black). This gives the king an escape square. However, creating luft costs a tempo and can create weaknesses, so timing this prophylactic measure correctly is an important skill.
Many tactical combinations exploit the back-rank weakness even when the final position is not checkmate. Threatening a back-rank mate can force the opponent to make concessions, such as giving up material to create an escape square. Always scan for back-rank threats before making a move, especially after trading queens.