Noun
queenside
(chess) The side of the chessboard nearest to the queen (at the opening position).
Castling is indicated by the special notations 0-0 for kingside castling and 0-0-0 for queenside castling. Source: Internet
If one player castles kingside and the other queenside, it is called opposite (or opposite-side) castling. Source: Internet
In queenside castling, the king is placed closer to the center and the pawn on the a- file is undefended; the king is thus often moved to the b-file to defend the a-pawn and to move the king away from the center of the board. Source: Internet
In addition, queenside castling requires moving the queen; therefore, it may take slightly longer to achieve than kingside castling. Source: Internet
It is common for both players to castle kingside, and rare for both players to castle queenside. Source: Internet
On the other hand, queenside castling places the rook more efficiently – on the central d-file. Source: Internet