What is Castling?

Castling is a special move in the game of chess involving a player's king and one of their rook pieces. It is the only move that allows a player to move two of their own pieces at the same time. The move has strategic importance, providing a way to safeguard the king from direct attack and connecting the rooks. In this move, the King moves two squares towards a rook on its initial square, then the rook moves to the square the king crossed. There are certain conditions for castling to be valid, such as no pieces being in between the king and the rook, neither piece having moved before, and the king not being in check.