A fork is a tactic whereby a single piece makes two or more direct attacks <simultaneously>.

Most commonly two pieces are threatened, which is also sometimes called <a double attack>. The attacker usually aims to gain material by capturing one of the opponent's pieces. The defender often finds it difficult to counter two or more threats in a single move.

The attacking piece is called the forking piece; the pieces attacked are said to be forked. A piece that is defended can still said to be forked if the forking piece has a lower value.

Besides attacking pieces, a target of a fork can be a <direct mating threat> (for example, attacking an unprotected knight while simultaneously setting up a battery of queen and bishop to threaten mate). Or a target can be <an implied threat> (for example, a knight may attack an unprotected piece while simultaneously threaten to fork queen and rook).

...

Forks can possibly <be escaped>. A forked piece such as the queen might check the enemy king, <a zwischenzug>, giving time to move the second forked piece to safety on the next move.

read further: Wikipedia article: Fork (chess)

check out: http://www.chess.com/article/view/t...

THE MOTHER OF ALL FORKS - A Guided Tour of Chess: https://timkr.home.xs4all.nl/tour/f...