What is this Google Wave thing that people are talking about? Simply put, it is a communication system, much like email but that the message remains in one spot (Google Wave servers) and grows as the discussions continue. So the message does not keep bouncing between recipients, but is one big communication source per topic.
Now that I have really confused you, the best explanation I have seen so far is this YouTube video by EpipheoStudios.com, which I think explains the concept really well. Take a look.