Check is when a piece (or multiple pieces) are attacking your King. If a King is in check he must get out of check before moving any other pieces.
There are 3 ways to get out of check.
- Block – to block a check you would move another piece in between the King and the piece attacking it.
- Capture – If the piece attacking the King may be captured with either the King or another piece then the player in Check may capture their way out of check.
- Run Away – The king may move to another square that is not being attacked by any pieces.
If a King is in check and you are not able to Block, Capture or Run Away to get out of check this means the King is checkmated and the game is over.
For more rules of chess visit this page the Basic Rules of Chess.