These positions tend to start the same way: White has no immediate tactical options, so he looks for checks and considers how Black’s replies to them would change the board. Here White’s only check is Re8. Black's only legal reply is Kh7. Now White asks the usual questions about the position that then would exist; he traces the lines out from the new position Black's king would occupy and sees that it would be aligned with his queen. White’s light-squared bishop is available to then play Be4, pinning the Black queen with protection from the rook. The queen is lost.