If a player cannot move any of his pieces including his king, and at the same time his king is not exposed to an immediate check, then this is called a stalemate. When a game is almost lost, it is desirable to achieve a stalemate situation and sometimes this is helped by the use a brilliant combination!
Help-mates are special chess problems in which the black and white co-operate in order to reach a mating position. When a problem states that white helpmates in 2 moves, both white and black make moves which will lead white to a mate in 2 moves. They usually have more than one solution.