What can you tell me about Quasimodo and the Cathedral of Notre Dame?

Ive recently been obsessed with the disney movie: The Hunchback of Notre Dame. But i want to know how much of the story is true, if any! Who was Quasimodo? Was he really Hunchbacked? Im going to see the actual cathedral next year with my cl, and i really want to know everything i can :] Mainly about the quasimodo thing! Any information will help. THANKS!