Mimesis, diegesis, and exigesis are, as noted by Robert Norwald, Greek loan words in English, meaning, respectively, imitation or mimicry, a recited narrative summary, and a recited narrative explanation. These are directly on point within the narrowly construed literary principles regarding show and tell and narrative voice and narrative distance.
Mimesis is show, a character voice experiencing a dramatic action; diegesis and exigesis are tell, a narrator voice telling a story, summarizing and explaining events, and oftentimes expressing commentary on the dramatic action. Narrative distance may be close in either or open, depending on who readers most closely associate with: narrator or character; and the degree to which narrator identity is developed as a dramatic persona. An anonymous narrator will be remote. An identifiably unique narrator will be close narrative distance, perhaps closer than the characters being portrayed, depending on setting, character, and plot development.
The two-voice theory of narrative theory implies there are distinctive, distinguishable, divisible voices in play: a narrator voice and a character or characters' voices. The degree of voices' gradation, however, are at extremes of solely narrator or solely character and any point in between. Artful voices tend to blend narrator and character voices in an attempt to avoid excessive tell.
Artful voices also tend to transition from extreme to extreme as story needs dictate. An unsettled narrative voice, though, flits from one to another extreme needlessly, often in the middle of a scene, without smooth transitions, similar to unnecessary tense or grammatical person shifts. These are the so-called point of view violations which plague struggling writers. "Violation," though, implies a law has been broken. No absolutes, any writing principle may be as artfully applied as artlessly applied: what works; what doesn't.
Seymour Chatman notes two manners of voice: narrated and nonnarrated; within the narrated category, several degrees of narrative distance, participating narrator, often a first-person narrator; invested narrator, perhaps not present in the setting of the action; and by degrees of omniscient narrator, from an objective omniscience of after-the-fact, when all is known, reporting, to a god-like omniscient omnipresence, definitely not present within the setting.
Nonnarrated narratives slip free of or estrange narrator voice altogether. Even a first-person voice may. The nonnarrated criteria is merely who addresses who how. Narrator addressing reading audience directly? Summarizing? Explaining? Expressing commentary? Narrated. Dramatic personas solely addressing one another or the self within the setting? Readers as vicarious participants or closeby bystanders experiencing the action along with the characters, not directly addressing readers? Nonnarrated.
Many narratives seamlessly transition between the two. Variety is the spice of life and of literature. Like with sentence variation: syntax, length, and impact; varying narrative distance by varying narrative standpoint may spice up a story. This is especially valid for narrated stories, so that narrative distance varies. A work may be composed entirely in a nonnarrated voice, remain in close narrative distance and still vary. Degree of psychic access varies then, from external stimuli to internal stimuli, from sensory perceptions of and external reactions to the outer world, to inner world thoughts and reactions, to deep personal thoughts and reactions.
The very nature of the wriiten word medium is summary and perhaps explanation regardless. It is impossible to fully imitate any iota of matter or being. A pastille candy cannot be imitated sufficiently by written word for a reader to comprehend its entire physical nature. If a reader has sampled a pastille, however, memory and imagination will fill in the gaps if there is sufficient imitation of the candy. The art then for a reader's benefit who hasn't experienced a pastille is to represent or imitate it so strongly, without being burdensome, that readers taste the candy.
Dusty old bones Aristotle, The Poetics of Aristotle, notes three areas that inform imitation or mimesis: medium, object, and manner. The medium is, of course, written word, prose particularly. The object is whomever or whatever the subject dramatic persona and action is. The manner is discussed above.