Ok, I haven't seen the movie myself, mainly because its Indie and only showing in the US, but I've gathered enough from trailers and background info that it is effectively the same as this setting being developed. There are two factions, the storytellers, who are responsible for dreams, and the other faction, responsible for nightmares.
The two warp in and out of the real world and dream world through some means, and while its extremely rare for the two factions to meet (For some reason), when they do, they fight. In dreams, and also in the real world (With improvised weapons, martial arts etc.). Both factions need to replenish their numbers from time to time, the storytellers recruit from people with vivid imaginations working on the assumption that any well adjusted human being will share their views, whereas the nightmare faction has some very strange initiation ceremonies to ensure that every single one of their recruits is committed.
Both factions are not quite human anymore, and are extremely limited in their capacity to influence or even interact with people in a waking state. However there do exist specialists on both sides capable of influencing people during daylight hours, individuals so valued they are kept around long after accumulating injuries that would make them otherwise useless within their factions, like lost limbs, blindness, etc.