Google Wave is a product that helps users communicate and collaborate on the web. A "wave" is equal parts conversation and document, where users can almost instantly communicate and work together with richly formatted text, photos, videos, maps, and more. Google Wave is also a platform with a rich set of open APIs that allow developers to embed waves in other web services and to build extensions that work inside waves.
Google Wave generating a tsunami of interest
I guess you saw that one coming. Check out the official Google Wave preview. Lots of hype that you can read about through this Google search. Since it's dependent on this protocol, don't forget to go over the Google Wave Federation Protocol to learn even more. This is what the Google Wave API says about Google Wave: