Esmeralda was a member of the Court Of Miracles. She was a dancer, also a very vital character, because she was the one, for whom all of the misfortune began. She was the love interest of almost every male main character (Gringoire, Quasimodo , Frollo, Clopin , and Phoebus.)
In the very end of the novel, it is revealed that Esmeralda was not actually a gypsy by blood. It turns out that she was born in Rheims, given birth to by a French woman, and was later kidnapped and brought into the gypsies as one of their own.
In the novel, Esmeralda is the love interest of almost every male character and is full of life and acts joyful.
In the opera, Esmeralda does not seem too joyful and is presented as a more serious and philosophical character.
In the animated film, Esmeralda is very joyful, childish even. She is described as a happy and carefree character, primarily because the animated version was targeted towards a younger audience.