It’s an interactive map that lets you zoom all the way from the sun and our solar system out to the Milky Way, including a view of 100,000 real nearby stars (there are 200 – 400 billion in the entire Milky Way). You can zoom and scroll around to get an idea of what our little interstellar neighborhood is like.
I viewed it in Chrome (which is what it’s designed for), and I hear it works in Firefox (that’s where I first heard about it) but I don’t know about IE.