In a fable, there will often be supernatural occurrences.  Characters are often animals that talk and act like people.  They are usually short stories and contain a lesson or moral about life.

In tall tales, the characters contain superhuman traits (Paul Bunyan).  Tall tales explain how something in nature came to be (Grand Canyon).  They often contain hyperbole (gross exaggerations) and similes (comparisons which use the words "like" or "as" to compare things)