A fork is a tactic in which a single piece attacks two pieces at the same time. As the attacking piece (often called the forking piece) is the protagonist of this tactic, it determines the type of fork. For example, in the following diagram:
we have a pawn fork (a personal favourite). While in the following diagram:
we have a knight fork. The knight is the most useful forking piece as it can attack two pieces without being a target at the same time, making it really hard for the opponent to defend.
If one of the two attacked pieces is the king, then the fork is called a forced fork. It’s possible at times to defend from forks with a zwischenzug (German word that means intermediate move) which is also an interesting tactic and will be discussed in a separate article.
All pieces can execute a fork, but it’s worth examining two special cases. First of all, the king can also be an attacking piece! It’s easy to lose an endgame by missing a king fork. As it’s hard to visualise, here is an example:
As you can see, the king is attacking the bishop and the knight at the same time (worth noticing that whoever needs to move, this is a draw!).
The other interesting case is the queen forking pieces. The reason is that, in most cases, the queen is more valuable of the attacked pieces which makes it harder for you to employ the queen in forks. A good tactic that you can run into often is a forcing queen fork, like in the following example:
The king is in check and needs to move so the queen can pick up the rook next!