What is Fianchetto?

A fianchetto (Italian: "little flank" ) is the development of a bishop to b2/g2 (for White) or b7/g7 (for Black), preceded by moving the adjacent knight's pawn one square (b3/g3 or b6/g6). The fianchettoed bishop commands the long diagonal and exerts powerful influence on the centre from the flank. The fianchetto is central to hypermodern and Indian Defence openings.