Stack Exchange is a network of Q&A sites on just about any topic you can think of that would have experts and enough questions to form a viable community. You can see new sites in progress on Area 51, the site for proposing new Stack Exchange Q&A sites.
You can also see the current list of Stack Exchange Sites.
However, the site you mention is a copy and is not affiliated with Stack Exchange or Stack Overflow in any way. Many of these copies sprung up in response to Jeff and Joel coming up with a really great idea and execution. However, these copies never really gained in popularity because no one, IMHO, has yet to implement Q&A better than Stack Exchange and Stack Overflow.
You can copy the technology, but you can't copy the people behind the scenes that use that technology to create great things.