Show bibles are updated with information on the characters after the information has been established on screen. For example, the Frasier show bible was "scrupulously maintained", and anything established on air — "the name of Frasier's mother, Niles' favorite professor, Martin's favorite bar...even a list of Maris' [dozens of] food allergies" — was reflected in the bible. The updated bible then serves as a resource for writers to keep everything within the series consistent.
Other show bibles are used as sales documents to help a television network or studio understand a series and are given to new writers on the writing staff. These types of bibles discuss the backstories of the main characters and the history of the series' fictional universe.