The pattern repeats. You are cultivating awareness of your mating threats, and for White the pattern here is familiar: the bishop at d3 attacks h7; if White’s queen also were to attack h7, he would threaten mate and Black would have to spend a move fending it off. So White plays Qe4, also attacking the bishop on e7. Strictly speaking the bishop isn’t loose, but it's attacked once (by White’s rook, then sitting behind his queen) and protected once (by Black’s queen). So White wins a piece.