Zatanna (Real Name Zelda Martino and Mystic Name Zatanna Zatara) is a sorceress and one of the most powerful magical beings on Earth. She is the daughter of famed sorcerer Giovanni Martino (the original Zatara) and one of the preeminent members of the Justice League.
The mystic world is separate from the mortal world, but as a sorceress, Zatanna coexists within both. As such, her human name, Zelda, is what she is known as to the public, but Zatanna is her name to the magical community. This stems from her family's ancient status as one of the most powerful magical lines. Zatanna, for instance, is a hereditary title held by the sorceresses of the family.
Zatanna's father was killed by dark sorcerers, and she dedicated her life to combatting magic in response to that tragedy. She was also left as the sole guardian of her younger brother, Zachary, and is thus very protective of him. Zatanna's magic is done in back speak.