What is Main line in chess?
The most theoretically important and commonly played continuation in an opening.
Main lines have been analysed deeply by many players and computers. Deviating from a main line is called playing a 'sideline' or 'variation.'
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- SidelineA less common opening variation that deviates from the most popular main line.
- Development leadHaving more pieces developed (off the back rank) than the opponent.
- En passantA special pawn capture of a pawn that just advanced two squares.
- CastlingA move that tucks your king to safety and activates a rook.
- Kingside castlingCastling toward the h-file, also written O-O, moving the king to g1 (or g8).
- Queenside castlingCastling toward the a-file, also written O-O-O, moving the king to c1 (or c8).