It's really, really, really completely up to the GM, including how true the information actually is. As it is, IMO, it's also completely useless with the help of the Divination skill.
For my part, it opens a door to the Dream Lands, where the caster can then travel as a High-Dreaming*. Where he can travel and how long he can stay depends on the level of the spell (from a random place related to a topic decided upon just before retiring, the mystical city of L’Aï-d’Jpur or any location of the Dream Lands where he wishes, though he must know about the location). From there, he can interact with the Dream Lands and their inhabitants, and try to gain whatever information he wants.
* People of the Dream Countries classify their inhabitants in five categories. First, you have the 'Dreams', the original inhabitants of the Dream Countries, aware they're there. Second, you have the 'Dreamings', who are the spirits of sleeping (and dreaming) inhabitants of the Plane of Reality, not aware they're dreaming. Third, you have the 'High Dreamings', Dreamings aware they're dreaming and who usually entered the Dream Countries with the purpose to find there something; the fortune-tellers, for instance, in quest for visions about the past or the future. Fourth, you have the 'Dreamers', inhabitants from the Plane of Reality who, one way or another, physically entered the Dream Countries. At last, you have the 'High Dreamers', entities shaping the planes of Reality and Dream according to their will; in other words, gods.