In chess a combination is a first sequence of moves that begins with a sacrifice. Here is a position for the game played by two students of mine in a class I did last Thursday and it was black's turn to move. Black has a queen, a rook and a bishop. White has two rooks a knight and a queen so white is a material but black to play can force to win by laying rook takes b2 check. Now after the rook takes the pawn check, the king absolutely has to take back. There is no other possible response. You can block this check, the king can't run over here to see one because the bishop will say check. So he has to take and after the king takes the rook, queen comes over to b4 and this is check mate.
So black wins the game by sacrificing material, its really his only way to get throughout the white position. First sacrifice powered by super win. Here is an another example of a small combination, in fact this is what's known as a made in two. White has the queen, the rook, the knight and the extra pawns. Black has the queen, the rook and the knight, but how does white actually win the game from here?
The White can make a small sacrifice, a big sacrifice the queen takes the rook check to the king. The king absolutely has to take the queen there is no way to block this check, the king cannot run backwards because of the other rook and after the king takes the queen black has rook to h8 check mate to the king. So white makes more sacrifice but then winds upon and the rook says check, the king cannot go here because he would be in check from the rook, he can'r go here check from the pawn as well as the rook, can't go here because of the pawn. It can't go here to g6 because of the knight. Game over, combinations can help us win from the positions what we can see away to get advantage.