What is a story bible?
A story bible is the source of truth for what is already established in a fictional world. An outline records what happens; a story bible records what is true.
A story bible is a reference source for the facts your novel establishes: characters, locations, world rules, timeline, relationships, terminology, and continuity.
The short definition
A story bible is an organized reference containing the facts a writer needs to keep consistent across a novel or series. Typical entries include character details, places, organizations, world rules, invented terms, relationships, chronology, and recurring objects.
Its purpose is retrieval. You should be able to answer a continuity question faster from the bible than by searching the manuscript.
Story bible vs outline
An outline is sequential: it tells you what happens and in what narrative order. A story bible is referential: it tells you what the story has established as true.
Mixing the two often creates a huge document that is bad at both jobs. Keep planned narrative movement separate from canonical reference information, then connect them where useful.
What belongs in one?
Include facts that would make a later scene feel wrong if contradicted. That usually means character identity and relationships, locations, world rules, dates and event order, organizations, terminology, important objects, and knowledge that different characters possess.
Do not add a field merely because a template offers it. A useful story bible is intentionally incomplete.
Put the idea to work in your draft
Good planning should reduce uncertainty and make the next writing decision easier. Use these steps to turn the ideas above into something concrete without adding unnecessary process.
Decide what this idea changes in your specific story before adding more detail.
Connect it to the chapter, character, event, plot point, or relationship it actually affects.
Write down the before-and-after state so the narrative consequence is easy to see during revision.
Use only as much structure as helps you make the next writing decision; stop before the planning becomes a second draft.