The narrator is the person who relates the events in the story or poem to the reader.  A story or poem usually has only one narrator, but there can be several narrators, particularly if the writer wants to communicate different perspectives and experiences of the same events to the reader.  It is important to recognise that although it is tempting to think that the writer and the narrator are the same, the narrator is, in fact,  a character created by the writer to tell the story.