You see that White’s bishop attacks Black’s knight, and also that White’s queen attacks the Black rook on d5. Hopefully you also see that QxR would put White’s queen at the top of a triangle that would include Black’s other rook at one point and Black’s king and queen at the other—a provocative pattern. Now identify the obstacle to QxR: the Black queen, which protects his rook. With the impediment clearly seen, you can be systematic in getting rid of it. How can White force Black's queen away from its defensive duties? With the decoy Re7, another flush attack. Black’s queen has no place to go that is safe and that allows it to keep guarding the rook on d5. So Black plays QxR, and then comes the significance of the triangular pattern mentioned earlier. White plays QxR+, which in itself only wins back the rook just sacrificed—but which also forks Black’s other rook and king, and wins the second rook after the king moves.