The diagram above is a typical example of back rank mate. White's king is trapped behind his own pawns, and is therefore stuck on the first rank. Black can deliver checkmate by playing Rc1++.
Back rank mates are easy to see, but in most cases they are also easy to prevent. In general, they occur only when a king has castled, there are too few defenders on the back rank, and the pawns in front of the castled king have not been moved.
There are several ways to avoid being the victim of a back rank mate. Keeping sufficient defense on your back rank will prevent any enemy pieces from safely attacking your king. In addition, if you are worried about a back rank mate threat, you can always move one of the pawns to give your king an escape square. For instance, if it were White's move in the diagram above, playing h3 would prevent the checkmate, as the king could now move to h2 if Black played Rc1+ on the next move.
