Fables, Tales, Myths and Legends

Fable is a fictitious narrative or statement as

• a legendary story of supernatural happenings
• a narration intended to enforce a useful truth; especially : one in which animals speak and act like human beings

Tale is a literary composition

• that has the form of such a narrative.
• that relates the details of some real or imaginary event, incident, or case; story

Myth is

• unproved or false collective belief that is used to justify a social institution.
• traditional or legendary, usually concerning some being or hero or event, with or without a determinable basis of fact or a natural explanation, especially one that is concerned with deities or demigods and explains some practice, rite, or phenomenon of nature. 
• an imaginary or fictitious thing or person.

Legend is

• a non-historical or unverifiable story handed down by tradition from earlier times and popularly accepted as historical. 
• the body of stories of this kind, especially as they relate to a particular people, group, or clan

Legend, fable, myth refer to fictitious stories, usually handed down by tradition (although some fables are modern).

Legend, originally denoting a story concerning the life of a saint, is applied to any fictitious story, sometimes involving the supernatural, and usually concerned with a real person, place, or other subject.

A fable is specifically a fictitious story (often with animals or inanimate things as speakers or actors) designed to teach a moral.

A myth is one of a class of stories, usually concerning gods, semidivine heroes, etc., current since primitive times, the purpose of which is to attempt to explain some belief or natural phenomenon.