A myth is a story told that is meant to teach a lesson, this story usually has been told for generations, and, while the story it is not true, the lesson can be quite valuable. A legend is a story that also has been told over generations, but it originated from something that was true (or believed to be true) however, this story may have been exaggerated and can not longer be proved.

A legend has at least a bit of truth to it, a myth is completely fictional.