An unconference is a participant-driven meeting. The term "unconference" has been applied, or self-applied, to a wide range of gatherings that try to avoid hierarchical aspects of a conventional conference, such as sponsored presentations and top-down organization.
Typically at an unconference, the agenda is created by the attendees at the beginning of the meeting. Anyone who wants to initiate a discussion on a topic can claim a time and a space. Some unconference sessions are led by the participant who suggested its topic; other unconference sessions are basically open discussions of the session topic.
An "unconference" is particularly useful when participants generally have a high level of expertise or knowledge in the field the conference convenes to discuss.