General stereo audio has two channels, left and right. So you can tell when something is on the left or right, but never very specific, if something's behind you and to the right it'll still just seem like it's right beside you.

3D audio has far more directions the audio can come from. If someone shoots a gun and they're behind you and slightly to the right, you'll be able to tell exactly where they are. Essentially an advanced version of surround sound with multiple digital speakers placed around you.

But it's all done with software, so you don't need any special headphones. Literally any set that's been made in the last 15 years will work, but obviously it'll sound better the better the headphones are.