What does castle means?
Castling is an optional chess move that involves one of a player's rooks and his king. In this move, the king is moved two squares toward the rook he intends to castle with, and the rook is placed on the square the king moved over to assume its final position. There are some restrictions, and they should be reviewed. Situations in which castling is not allowed: 1. If the king or the rook being used in castling has moved. 2. If the king is in check, would have castled through check, or would castle into check. 3. If there are any other pieces between them. Castling, the only legal move where two pieces move simultaneously, is notated as 0-0 if you are castling king side (the rook is only 3 spaces away) or as 0-0-0 if you are castling queen side (the rook is 4 spaces away).