Fork
One piece attacks two things at once. They can only save one.
Example
The knight can attack the king and the rook at the same time.
- 1. Nc7+: Check, and the rook on a8 is attacked too: a fork.
- 1... Kd7: The king has to move…
- 2. Nxa8: …and the rook falls.
Practice the fork free on ChessScout.net