Forking can sometimes be terrifying to see and very dangerous too this could also work with a pawn (FORK PAWNS). Getting forked happens very often and it is one of the most common tactic. In the following position I will show what a fork is:
As you can see that the knight is checking the king and at the same time attacking the king. So, when the knight, bishop, rook, and queen double attack like this then it is called a fork. It always doesn't have to be checking the king and attacking another piece it could also be like:
Here the bishop is attacking the two rooks and can at least one of them. The rooks cannot check the king on a8 because the bishop on c6 is defending that square. Most of the time a fork involves a king (BUT NOT ALWAYS THE KING HAS TO BE INVOLVED IN A FORK).