Doing a little research and patiently waiting for my Google Wave invite, I wanted to get a better understanding.
Google Wave is a real-time collaboration platform. The easiest way to describe it would be a blend of Twitter, Flikr, YouTube and Word all in one interface.
It looks to be very early in development and Google is making it open source to accelerate the evolution of the product.
At this point, by just reading about it and watching demo videos, it doesn't seem to have the impact that Twitter or YouTube. But, it will be interesting to get in there and use it and watch it mature.