Black’s bishop is loose, so White’s energies turn to ways it might be attacked while also giving check. It can't be done from the current position on the board; White’s only check with the queen, 1. Qc8, doesn’t attack the bishop. But it does push the king to h7—and then might a double attack be possible? Keep your eye on the loose bishop, which you are working to capture; and examine every check that would be available after the king moves, looking for a double attack. 2. Qf5+ wins the bishop.
Notice the importance of not rushing off to examine checks with other pieces, such as White’s knight, in order to help arrange a queen fork; sometimes the queen can do all the work by itself, as it does here. (With Black’s queen poised to give check, White wouldn’t want to go forward with this sequence without making sure his own king will be safe at the end of it; the fork will cause White's queen to be taken far away from its king and leave it out of position to supply defense. But White would have a decent reply to Black's Qg1, Qe1, or Qc1, so the coast is clear for the fork.)