A narrator is, within any story (literary work, movie, play, verbal account, etc.), the non-fictional or fictional, personal or impersonal entity who tells the story to the audience. When the narrator is also a character within the story, he or she is sometimes known as the first person. The narrator is one of three entities responsible for story-telling of any kind. The others are the author and the audience; the latter called the "reader" when referring specifically to literature.
The author and the audience both inhabit the real world. It is the author's function to create the universe, people, and events within the story. It is the audience's function to understand and interpret the story. The narrator only exists within the world of the story (and only there—although in non-fiction the narrator and the author can share the same persona, since the real world and the world of the story may be the same) and present it in a way the audience can comprehend.
A narrator may tell the story from his or her own point of view (as a fictive entity) or from the point of view of one of the characters in the story. The act or process of telling the particulars of a story is referred to as narration. Along with exposition, argumentation, and description, narration (broadly defined) is one of four rhetorical modes of discourse. More narrowly defined, narration is the fiction-writing mode whereby the narrator communicates directly to the reader.
The concept of the unreliable narrator (as opposed to "author") became more prominent with the rise of the novel in the 18th century. Until the late 19th century, literary criticism as an academic exercise dealt solely with poetry (including epic poems like the Iliad and Paradise Lost, and poetic drama like Shakespeare). Most poems did not have a narrator distinct from the author. But novels, with their immersive fictional worlds, created a problem, especially when the narrator's views differed significantly from those of the author.
Perspective, interpretive knowledge, focalization and structure are the narrator's characterisa viewpoint character is Dr. Watson from the Sherlock Holmes stories. Almost all of the Sherlock Holmes collection is from his point of view.