Black has a king and queen adjacent to each other on a diagonal. The position seems to call for a skewer, and would be easy if White safely could run a bishop through the two Black pieces; he would be happy to trade his bishop for a queen. But if the bishop goes to e5 it gets taken by Black’s king, and if White’s queen instead goes to the needed diagonal Black plays Kc6 and White can do no better than a trade of queens. White needs a way to pry Black’s king and queen farther apart before his own queen skewers them, so that Black’s king can't make it back to provide protection. How to achieve this? By playing those skewers just described in succession. First comes Be5+, which invites Black to play KxB. Now that the king is two squares away from its queen, the skewer with White’s queen (Qf4+) works fine, thanks to the protection furnished by the pawn at g3.