Castling is a special move in chess involving the king and one of the original rooks. It’s the only move that allows a player to move two of their own pieces at the same time. Both pieces move simultaneously in a specific way. It's performed to improve the position of both the king and the rook.
When a pawn reaches the opponent's back rank, it must be promoted to any other piece (except a king), regardless of whether that piece was previously captured. Most players choose to promote a pawn to a queen because it's the most powerful piece.
En passant is a unique pawn capturing method. When an enemy pawn moves forward two squares from its starting position and lands beside a player's pawn, the player can capture it as if it had moved just one square. This move must be done immediately after the enemy pawn's double-square advance.
