From the event website:
Well, first of all, if you don’t already know what it is, an unconference is “a participant-driven meeting.”
What does that mean? It means rather than a committee or board deciding what the all individual aspects of a conference will be — the focus, topics, speakers, menu, etc. — a small group of people kick off the planning, and then open it up to the community at large to shape the event. In other words, our team is getting the venue, dates, key sponsors, and first participants together, and then opening up the floor for suggestions for speakers, specific sessions, etc.
Essentially: It’s an opportunity to trade your knowledge for that of others. If you have a piece of the puzzle, suggest a session where you can share it, and then if enough people sign up to attend the session, you’re on.
Why does it work? Because rather than charge high fees to pay speaker/experts, everyone gives a little — whether it’s your time as a speaker or volunteer or a reduced ticket price.