Again White’s bishop already has a clear path to g8, so White seeks a way to open the h-file, this time for the benefit of his queen. If he takes the h-pawn with his knight, Black is not in immediate danger and can play RxB. The desired effect is gained differently: White starts with 1. Qh5, threatening mate with Qxh7. Black’s only way to fend it off is by pushing his h7 pawn to h6. Now White plays 2. Qg6, occupying the hole left by the advance of Black’s pawn—and still threatening to mate on h7. Black has nothing but h6xN, which leaves the h-file entirely open. White’s queen has lost the cover that the knight threatened to supply, but no longer needs it: Qh5# is mate.
Again a knight helps open the needed file. The little back-and-forth movement of White’s queen is a useful tool, worth examining until it's familiar. Notice that now we have two techniques for prying open the king's pawn cover. One was to put a threatening piece on a square where one of the pawns was obliged to make a capture; the other, here, was to make a mate threat (most classically with a queen) against a square where one of the pawns sits. Often a pawn so targeted will step forward to gain some protection from its fellows, creating a hole where your queen can go. The general theme is one we have seen many times before: mate threats are a common way to force the pawns in front of the king to move, thus opening lines you can use for other purposes.