White’s knight is on a light square, as are Black’s king and queen, calling for consideration of a fork at b6. Black guards the square with the pawn at c7, which (a brief examination reveals) cannot be pinned, captured, or effectively distracted. White nevertheless imagines playing the fork and losing the knight. With the knight off the board and Black’s c-pawn moved to b6, is anything interesting possible? White has one check―Qe8―but it just loses the queen. He has no more knights he can use to fork anything. But here as in the previous example he sees that Black’s king and queen are on the same line—this time a diagonal. He thinks “pin,” again, and can impose one with Be6, winning the queen. (Black replies Ne5, which will allow him to retake White's bishop after BxQ; then White has Qxg6.)
Here the key thing to visualize was White’s own knight cleared from the board. The alignment of Black’s king and queen already was present; the fork serves just as a way for White to move his knight out of the path of his bishop, and in a manner that forces Black’s response before he can take measures to avoid the pin that follows. One of our general points repeats: in addition to examining every check you would have after an exchange, look for any newly open lines that might allow for a pin or other tactic.