What is Flank Opening?

A Flank Opening is a type of chess opening in which the game is not characterized by specific moves, but rather by a pawn move to the side of the board – typically b3, b4, g3, or g4 for White, or b6, b5, g6, or g5 for Black. This is in contrast to the open and semi-open openings, where the game usually commences with action in the center of the board.