Edgar Rice Burroughs was not satisfied with creating characters and events within the world that we know; instead he created whole new worlds for histories, and he filled them with peoples, languages, cities, wars, plants, machines, and monsters that were believable to the reader, yet still alien and fantastic enough to thrill and delight.

From A-Kor, the keeper of the Towers of Jetan in Manator, through Zytheb, one of the priests of Brulor in Ashair, this is a comprehensive reference to the fantastic worlds of Burroughs. Each entry provides a complete definition, along with a reference to the book in which the entry appeared. For terms, the language, either actual (e.g., Latin and French) or Burroughs-created (e.g., The Tongue of the Great Ape or Pal-ul-don), from which it was derived is given.