Fianchetto
A fianchetto develops a bishop to g2 or b2 (g7 or b7 for Black) after advancing the neighbouring pawn one square. From there the bishop commands the long diagonal across the whole board and shields the castled king. Trading off a fianchettoed bishop tears a hole in the pawn cover, so releasing that tension deserves a hard look.
Both sides have fianchettoed: the bishops on g2 and g7 stare down the long diagonals toward b7 and b2.