Story structure
Exposition
The insertion of background information into a story, delivered directly by telling or indirectly by scattering facts through scenes.
Exposition is "the insertion of background information within a story or narrative": the delivery of the facts a reader needs to follow what happens. The direct form halts the story to tell, a narrator's summary or a told backstory. The indirect form, nicknamed "incluing" by the writer Jo Walton, scatters information seamlessly through the text, in dialogue, flashbacks, characters' thoughts, background details or in-universe media, so the story never pauses. The article credits Rudyard Kipling's stories and names Robert Heinlein among the writers the technique reached.
Exposition is why openings are hard. Too little and the reader is lost; too much and the story stalls, the complaint known as the info dump. The standard fixes are all incluing: cut what the reader does not yet need, and deliver the rest in the thinnest slice that keeps the scene moving. Let backstory surface when it becomes relevant; see show, don't tell.