It's "augmented reality", so multiple people can walk around and see the display from all angles at the same time. So it's beyond stereoscopic, but it's not a traditional hologram. (It's much better than the Tupac "hologram" which was a single 2D image!)

It works by stereoscopy. There maybe something "holographic" in the math used to compute what to show each eye, but there is no projection of light into space to form holographic images that people can walk around.

I doubt it actually has a holographic display; I assume that processing power of those glasses isn't enough and current display don't have high enough resolution yet. But then again the following description could be a holographic display (or it could be a description of antireflective coating -- those dumbed down explanations are sometimes worse than useless)

> To create Project HoloLens’ images, light particles bounce around millions of times in the so-called light engine of the device. Then the photons enter the goggles’ two lenses, where they ricochet between layers of blue, green and red glass before they reach the back of your eye. “When you get the light to be at the exact angle,” Kipman tells me, “that’s where all the magic comes in.”

the demo looked very holographic

mostly marketing