The proper use of narrative and exposition in short stories and novels is one of the keys to writing successful fiction and using fictional techniques.
Narrative: is the objective reporting of your story, that which can be pictured visually in concrete images in the reader’s imagination. It is what the characters do in the action of the story.
Exposition: is information, often interpretive and/or subjective funneled through the viewpoint character, to shed light on the action. It includes comments, opinions, reactions, explanations, and feelings (Definitions by Carole Gift Page, used with permission).
Faulty exposition interrupts the narrative flow, shatters the illusion of reality, and embarrassingly reveals the mechanics of fiction writing just like a playwright jumping on stage and interrupting a play during a performance.