Fishbowl is when only a part of the group is actively involved in a process while the rest of the group watches – like someone watching fish in a fishbowl! It can be used in large groups, when only part of the group needs to have an active role. A coherent discussion can happen with many being able to listen.
People from the quiet, “outer” circle can signal that they want to participate in the discussion (e.g. by standing “in line”), and people from the inside circle can choose to give up their chair in favor of someone from the outside.