The same idea once more. The first thing is to train your eye to see two pieces lined up with a single square between them, as Black's queen and knight are arranged in this case. White can’t get a pawn to e5 in one move, but he can do it with a two-step push: e3-e4 forces the bishop to move because the pawn is protected three times (count 'em). Now e4-e5 wins the knight after the queen moves; this time the rook on e1 provides the needed cover.
Black has no effective counterplay here, but as an exercise imagine the position with White’s pawn on h3 moved back to h2. Can something so subtle make a difference? It does: for then after 1. e3-e4, Black has 1. …Ng4—threatening mate with Qxh2. The mate threat can be evaded in various ways (e.g., with 2. BxN, BxB; or with the simple 2. e4-e5, forcing Black’s queen to retreat), but now the forking threat is over because Black's knight has left f6.
There are a few lessons to take away from the variation just discussed. Again, especially when you are not operating with checks you have to ask what threats (particularly what checks and mate threats) your opponent might be able to make as an alternative to playing into your hands. In this case you would want to be especially wary of moves he can make by either of the pieces being threatened, and wary as well of threats against your king's position. If an enemy queen already is aimed at a square next to your king, as Black's is here, remember that your opponent may be able to create a mate threat by simply adding another attack against that square. Maybe the mate threat can be defused easily, but it will cost you time. Finally, you can treat this as a little study in the value of a well-placed pawn. In the position as actually diagrammed, the pawn on h3 is doing quite helpful work by keeping Black's f6 knight from jumping to g4. This is an important office of pawns: guarding squares where you don't want enemy knights planted.