A story begins at a certain place and time; say, a fellow sitting on a bench at a bus stop, waiting for a bus.
The story then delves into flashbacks of the fellow’s life leading up to the time when he found himself sitting at the bus stop; say, his childhood in rural Alabama, his involvement in the Vietnam War, his business ventures. The story then takes over from that point.
Anyway, is there a term for this? Eliptical storytelling, perhaps?
That sounds like in medias res.
Ooh, if I can hijack, another question about storytelling: What do they call it when the music for a scene is intentionally mismatched to the content of the scene, for maximum impact?
Examples include a sci-fi salsa piece playing while one of the good guys is getting his head kicked in by thugs in an episode of Crusade, the Hallelujia Chorus in Neon Genesis Evangelion, and the Mooby the Cow theme song in Dogma.
Those sound like juxtaposition, even though they don’t exactly match any of the examples given. I don’t think it’s meant to be an exhaustive list.