What is Flank?

Flank refers to the side squares of the chess board, particularly the files from the knight's file to the rook's file. These include the 'a', 'b', 'g', and 'h' files. Moving pieces on these squares or targeting these areas is known as flank play. Flank openings are named because they involve the development of pieces to these squares or strategies that focus more on these side sections of the board.