That last position involved a flush attack on the queen: White planted a rook right next to it. Let us continue to look at this theme more closely. The logic of it is no different than in the previous set of positions; we study these cases separately just because the act of moving a piece up next to the enemy queen without any protection can seem counterintuitive. It is useful to see a bunch of positions where this is done deliberately and productively so that you will feel at home with it.
We start on the left with a simple case. Identifying White’s double threat against a square adjacent to Black’s king should be no trouble: he almost can mate with Qg7. What prevents this is Black’s queen on f8. The natural thought is to do something to pressure or dislodge the guard. White has one way to attack Black’s queen without disturbing his mate threat: he plays Re8, sticking a rook flush against the queen and thus putting the queen into an untenable position. Now analyze Black’s possible responses and their consequences; in response to each of them consider what checks you could give—or whether you can mate. If Black plays QxR, White mates with Qg7; indeed, since Black’s queen now is pinned, the only way he can avoid being mated on g7 next move is by playing Kf7—in which event he instead is mated with QxQ. To repeat: in a sense this is just another case like the most recent batch; a queen guarding against mate is attacked. Our particular goal here is just to get used to the practice and the sight of planting a loose piece right next to an enemy queen. It looks strange at first but is a useful device.