Chess: Tactical nuances, and tricks

A position from a game I played just now, my opponent here missed something, he played quickly.
What he did was Nxe5?
That is normally the move in this position but only when whites bishop is not undefended on d3.




A little later in the game the following position came up

I played Nxc4 leading to this position

Here he decided to take the bishop I just left undefended, I did not have much choice, and I suppose taking the bishop is the move, but I had a small trick.
1.Qxg4 Ne3
thus I made a fork and thus I still have more material, in this forced combination I netted a pawn.