From Indie Games: Backstory by whom?, comes this useful division by Ron Edwards.
Four authorites that may be divided among players and GMs:
Content authority – over what we’re calling back-story, e.g. whether Sam is a KGB mole, or which NPC is boinking whom
Plot authority – over crux-points in the knowledge base at the table – now is the time for a revelation! – typically, revealing content, although notice it can apply to player-characters’ material as well as GM material – and look out, because within this authority lies the remarkable pitfall of wanting (for instances) revelations and reactions to apply precisely to players as they do to characters
Situational authority – over who’s there, what’s going on – scene framing would be the most relevant and obvious technique-example, or phrases like “That’s when I show up!” from a player
Narrational authority – how it happens, what happens – I’m suggesting here that this is best understood as a feature of resolution (including the entirety of IIEE), and not to mistake it for describing what the castle looks like, for instance; I also suggest it’s far more shared in application than most role-players realize