There are a lot of options that you have when your opponent starts out with d4 and one of the most common responses is Nf6. White typically will respond developing one of his knights to the 3rd rank.
The trap comes when white starts out with Nd2. Here black is going to give up a pawn with e4 and then will move Ng4, attacking the pawn on e5.
If white falls for the trap and tries to kick the knight off the g4 square with h3, white will either lose the game immediately or lose lots of material.
Even if white doesn’t fall for the trap, black still has a lot of different options to keep up the pressure and there are still many attacking lines for black to attack and can easily get the material back that he gave up early on in the game.
Watch the video below to see a detailed explanation of this trap.