Expert: Tony D'Aloisio - 1/11/2012

Question
Hello Tony D'Aloisio,
I want to know what is castling and in which situation castling is made?

Answer
Castling is the only move which involves two of your own pieces at the same time.  You can either castle on the kingside or the queenside.  In order to castle, the following stipulations must be met:

1) the king and rook in question cannot have moved previously;
2) there can be no other pieces (your own or your opponent's) in between the king and rook;
3) you cannot castle out of check, through check or into check (however, it is legal to castle if the rook in question is attacked or passes through an attacked square [in the case of queenside castling]).

The following instructions are from White's point of view (if you are playing the Black pieces, reverse the directions; i.e., right becomes left).  You castle kingside by moving your king two squares to the right, then moving that rook two squares to the left, so that it ends up on the square next to the king (on the other side).  Castling queenside involves moving your king two squares to the left, then moving that rook three squares to the right, again so that it ends up on the other side of the king (and next to it).

Castling is usually done by both players as early as is convenient, in order to get the king into safety and bring into play ("develop") the corresponding rook.  Sometimes it can be delayed (or even forsaken altogether) to advantage, but this course is only to be recommended for the advanced player, as it can involve a considerable amount of risk to leave one's king exposed to attack in the middle of the board.