A narrator is a person who tells a story to an audience. Narrators occur in face-to-face story-telling, and in literary works, movies, and plays. They can be fictional, or they can be real people. When the narrator is also a character within the story, he or she is sometimes known as the viewpoint character. The narrator is one of three parts in any story-telling. The others are the author and the audience; in literature, the latter is the reader.
The author and the audience both live in 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 presents it in a way the audience can grasp. In non-fiction the narrator and the author may be the same person, since the real world and the world of the story may be the same.