The idea of this chapter in simple form. There are two ways to see it. The first is to do the usual scan of the lines leading out from Black’s king. You see a pawn on e5 that can be pinned to it. As in the last case you consider an upgrade by substitution. Here the pawn’s only guardian is the queen on f6, which would make a superb target for a pin; so White plays Nxe5. If Black is foolish enough to reply Qxe5, White has Re1, a classic pin of the queen by White’s rook. Black takes the rook with his queen; White replies QxQ and has won a queen and a pawn for knight and a rook—a good trade.
The other way to see the idea is to experiment with captures and their consequences. Thus White plays Nxe5 in his mind’s eye, imagines Black replying QxN, and notices that this puts Black’s king and queen conspicuously on the same line. The general lesson is to think through any captures you can make—in search not just of immediate profits but of alignments left behind afterwards.