"Wave is what Google call a "a new tool for
communication and collaboration on the web". Think of it as a cross
between e-mail, social networking, IM, IRC and Twitter. It not only
gives (or to be fair will give) ways to communicate but gives
instant feedback to other participants. Using the basis of a wave
as a conversation, it allows others in your conversation to see
what you are writing in real-time, as you write it. No more having
to wait while your IM buddy finishes her message. Wave also allows
-- in the same tool -- bulletin board-style messaging for
participants to follow when they log back in. It has nice features
which permit you to respond to different parts of a message in-line
and in-context. New participants can be brought in at any time and
not only get the full history of the "wave" but can "playback" the
wave as it happened, seeing who wrote what when and in
chronological order."