At many conferences, the most useful exchange happens when someone discovers another attendee working on the same problem. An unconference brings that possibility into the program itself. Participants propose sessions and help create an agenda responsive to who has actually arrived.
An unconference invitation can be a question, a demonstration, a workshop, or a conversation. Proposing a session need not mean claiming to be its expert.
Imagine a gathering of independent museums. Someone could offer a demonstration of a cataloging approach; someone else could ask for help welcoming school groups. Participants choose according to the knowledge they can contribute or the problem they want to explore.
The freedom still needs infrastructure. A visible schedule, usable rooms, time boundaries, and a way to handle overlapping topics keep initiative from becoming confusion. People unfamiliar with the format may need examples and encouragement before they realize that they can propose something.
Popular sessions are not necessarily the only valuable ones. A small discussion among three people facing an unusual constraint may be more productive than a crowded talk. Judging the event only by audience size can recreate the incentives of a conventional conference. The distinctive opportunity is to connect particular needs and capabilities, including ones the organizers could not have known in advance.