Unconference

An unconference, also called an Open Space Conference, is a participant-driven meeting. The term "unconference" has been applied, or self-applied, to a wide range of gatherings that try to avoid one or more aspects of a conventional conference, such as fees, sponsored presentations, and top-down organization - wikipedia

Open Space Technology (OST) is an approach to purpose-driven leadership, including a way for hosting meetings, conflict minded peacebuilding, conferences, corporate-style retreats, symposiums, and community summit events, focused on a specific and important purpose or task — but beginning without any formal agenda, beyond the overall purpose or theme - wikipedia