What is the purpose of the introduction to The Pearl?

The introduction to The Pearl not only serves to set up the plot, but also lets the reader know that the story is a moral lesson, a "parable," based upon a folk tale. The repetition of 'they tell' and the use of 'they say' adds to the element of the oral tradition that lies within the heart of folk tales. It introduces the three main characters in the novel, Kino, Juana, and the ill-fated child, Coyotito. The reader also is warned that this will be a tale of both 'good' and 'bad' ; most folk tales and all parables teach a lesson. Thus, this introduction also serves to let the reader know that a lesson will be learned by the end of this novel.