A Dream Plane is a separate world created in dreams.
Terran 8 has an extensive permanent Dream Plane established and controlled by the Ancients [beginning before the Proto-Paragangian Exodus ] Dream Plane Portals are given to the leader of the Dragons and the Dream Keepers of D'zeron , who are then held responsible for contoling the access of their people to the dream Plane.
There is another dream plane on Terran 8, associated with Jonathan Landon and his children called the Dream Wind. From the wind one can observe the Ancients dream plane but those on the Ancients dream plane cannot see those on the wind. It is however not a complete lifelike dreamworld, but instead a foggy place with vague representations of the surrounding dream planes.
A small temporary dream plane is created when two or more people share a dream. The more people participating, the more lasting the dream plane, however all the people involved have to be there for the plane to emerge. Desmond is trapped in a dream plane of this sort formed by himself and Alexandreil [and someone else??? perhaps it has to be Alexandreil under the control of Thearon ? perhaps it has to be a wind plane?--I need to work out the details on this] . Chathalen is then trapped on the same dream plane by defending Harris and Jason from Alexandreil under the control of Thearon. Desmond is unconscious as long as Alexandreil is not dreaming on the station[under the control of Thearon?--it can't be just Jonathan, because he would dream on the station all the time. although, it could require Wind Walking, which Alex would have no reason to do there and would avoid if it cause Desmond to become dream bound] but when Chathalen and Alexandreil join him on the plane there presence as dreambound creatures is enough to render the plane permanent and thus Desmond regains consciousness as a dreambound creature.