I'll try to give a real answer:
The goal was to replace email. The result is a cross between email, threaded discussion, wiki, and instant messaging. (no, really. Live concurrent collaborative editing, along with a rewind feature so you can review the chronology in a more logical fashion) One can make gadgets that show up in a wave and allow you to interact in ways besides just typing, and there are also bots that interact with waves much like a normal user. Instead of adding some spell check the way you might normally think of it, they have a spell check bot that uses the wave collaborative editing features to highlight and potentially change your spelling. (which means someone else in the conversation could finish up doing the editing the spell check highlighted in a sentence earlier in your paragraph)
It works somewhat like email, as in once things settle down whoever can run their own wave server. And it could be integrated with, say, a blog where the comment section of a post would be a wave. (and have all that functionality, and stuff)