Kingside castling is a defensive move that typically happens earlier in the game. The king moves two squares towards the h-file (to g1), and the kingside rook jumps over to f1.
This is the more common form of castling because: • It can be completed more quickly (fewer pieces to move out of the way) • It places the king in a slightly more protected position • The rook is well-placed to control the center files
Queenside castling is a more complex maneuver where the king moves two squares towards the a-file (to c1), and the queenside rook jumps over to d1.
This form of castling: • Usually takes longer to set up (need to move queen and bishop) • Can lead to more dynamic play • Places the rook closer to the center • Often used in positions where kingside castling is prevented
Requirements for Both Types of Castling:
• The king and the respective rook must not have moved previously
• No pieces can be between the king and the rook
• The king must not currently be in check
• The king must not pass through a square that is under attack
• The king's destination square must not be under attack