Zwischenzug

During an expected series of exchanges one opponent makes an unexpected move that creates a new threat, thus breaking the anticipated exchange.

As a result the person who makes the zwischenzug gains a material advantage.

The word "zwischenzug" is German for "in-between move."

In this example after the d6 black pawn captures the e5 white pawn we would expect an exchange of queens. Instead, by placing the black king in check with the c4 bishop white makes it possible for the white queen to capture the black queen without being in danger herself!