What is a wave?

• Instead of emails being passed along, a Wave is a hosted conversation, with only one copy that anyone can contribute to. So I can write content similar to an email with richly formatted text, photos, videos, maps, and more and then invite any number of recipients to view it, and reply...
• A wave is equal parts conversation and document. People can communicate and work together with richly formatted text, photos, videos, maps, and more.
• A wave is shared. Any participant can reply anywhere in the message, edit the content and add participants at any point in the process. Then playback lets anyone rewind the wave to see who said what and when.
• A wave is live. With live transmission as you type, participants on a wave can have faster conversations, see edits and interact with extensions in real-time.

How to get Google Wave Invite?