This special move allows a player to do two important things all in one move: get the King to safety (hopefully), and get the Rook out of the corner and into the game.
Castling 1: The player moves his King two squares over to the right side and then moves the Rook from that side's corner to the left hand of the King.
Castling 2: The player moves his King two squares over to the left side and then moves the Rook from that side's corner to the right hand of the King.
Regardless of which side, the King always moves only two squares when castling.
In order to castle, however, it must meet the following conditions: it must be that King's very first move; it must be that Rook's very first move; there cannot be any pieces between the King and Rook to move and the King may not be in check or pass through check.
Check and Checkmate
Checkmate happens when the King is in a position to be captured (in check) and cannot escape from capture.
If a King cannot escape checkmate then the game is over.
Customarily the King is not captured or removed from the
board, the game is simply declared over.
There are only three ways a King can get out of check: move out of the way (though he cannot castle), block the check with another piece, or capture the piece threatening the King.
Occasionally chess games do not end with a winner, but with a draw.
Ajedrez - Chess