To be a true folk tale, a story must have its origins in what we call the oral tradition. This means the story was first passed down orally by storytellers. Along the way it may have had things added or subtracted as each storyteller made it his or her own. It eventually was written down, which is why you're able to read it in a book now, but it wasn't written down first. For example, Paul Bunyan reads like a folk tale and has many folk tale elements in it, but it is not a true folk tale because it was a written story to begin with and not something passed down through the generations orally.