When the rival takes a piece, the natural thing is to take it back at once. But sometimes there is something better first: an , almost always a or a threat, that the rival has to answer. Here the black queen has just taken on d2. Instead of taking her back now, the rook on e1 takes on e8 with check; the king steps aside, and only then does the other rook take the queen back. White wins a whole rook.