Answer:
A narrator guides the story for the reader.
A narrator may know the thoughts of characters in the story
A narrator may be a character in the story.
Explanation:
The narrator's main purpose in a story is to be the guiding force for the reader in the story. This is done by explaining the subtle nuances of the scene and the emotions of the characters, such as what they are thinking and feeling. The narrator can be a person outside of the story looking in from a larger perspective or it can also be a character in the story, even the main character at times.
