I have the feeling Google Wave is something you're gonna have to use to really understand: In the simplest terms, it's a live chatroom with a spread of documents, photos and/or videos, where you can reply to any part of any message or anything that's shared, and it's all real-time.
The idea is to drag email and IM into real-time—so it's free-wheeling mesh of Twitter, IM, Friendfeed really, any other kind of service presenting semi-real-time stuff in a stream. But in Google Wave, you can share and collaborate on projects, and all of this is mashed together at once, so it might be the ultimate service for people with ADD, or enterprise looking to simulate the feeling of 10 people standing around a desk scattered with a bunch of projects, but you're all able to work on any of them simultaneously while you're also whispering to the cute girl across the table about the new sushi place around the corner. You start a wave with any message or photo or whatever, and you bring people into the discussion, and then they can bring other people in as well (unless you block it or start kicking people out) so it's as public or private as you want it to be.
It's easy to see why Google would jump in here—real-time is the next iteration of the internets, and everybody's been obsessed with it since Twitter (look no further than Facebook). Not only does Wave elevate the collaborative and conversational aspect of real-time, Google's smartly pimping it from the app side too, pushing for apps that use and run within a wave, since a service is now really only as good as it is as a platform. At least, I think that's what this is all about. Maybe it's just a surfing chatroom. [Google Wave, Cnet]