I tell my students to go out and interview someone and let them struggle with this for a while without giving them much sense of direction. They have already learnt that narration is writing that moves through time and space. Its primary function is to tell a story or describe an object, place or event. Exposition is writing that explores, explains or analyzes facts or concepts. I explain that these four rhetorical strategies like the four points on the compass help the reader and writer find and define their position.
Narration is necessary to provide setting and context.
Exposition is necessary to provide depth and analysis. Direct quotations give immediacy and life to the interview while indirect quotations help summarize large pieces of information that may become too bulky. I am not sure how the idea came to me, but I really have not had much of a handle on this genre and have not liked teaching this essay for that reason. In reality the best forms of analysis come in the forms of narratives as in novels, short stories. Narrative, according to my definition, describes an event and object in time and space while exposition analyzes, argues and interprets in other latitudes.