This forum tends to use the words 'Folk' and 'Traditional' synonymously, but I think that's an error.

Traditional has an element of endurance over time in association with an identifiable social group. For example, my family traditionally goes to my Grandparents house for christmas.

On the other hand, folk doesn't necessarily have to meet a temporal standard, just some minimal level of association with a social group, and a general lack of formality. A mountain storyteller can make up a new tale and tell it to some children, and its probably fair to call it a folk-tale at the moment of its creation. On the other hand, it would not be fair to call Huckleberry Finn or Moby Dick folk tales, no matter how long those tales are retold. They are formal works of fine art, written for publication.

Of course there's an arbitrary element to any definitions of this kind. I'm reminded of a comment of a classmate back in the 1970's. There are two kinds of food in the world. Rich peoples food, which is called GOURMET, and poor peoples food, which is called ETHNIC.