SUMMARY:

Castling is when the king moves two squares towards the rook, and the rook moves to the other side of the king. This helps keep the king safe. Castling can only be done when the path between the rook and the king is empty, the king is not under attack, and the rook and the king have not yet moved in the game. These three conditions form the acronym KKR: Khali Maidan, Khatre se bahar, and Ruka hua.