Back Rank Mate:

This mate occurs when a Rook or Queen checkmate a king that's trapped behind his own pieces (usually pawns) on the 8th rank. This type of checkmate usually happens in amateur games where one opponent becomes a little careless about the safety of his king, and the opponent manages to find his way to the 8th rank and trap the king. In the example below, black forgets to create an escape square for the black king and White slides his rook over to the 8th rank and checkmates him.