> ## Documentation Index
> Fetch the complete documentation index at: https://docs.voiceflow.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Knowledge and data

> The knowledge base, data sources, variables, secrets and redaction: what an agent reads, writes and protects while a conversation runs.

| Term                                                                   | What it is                                                                                                                                |
| ---------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| **[Knowledge base](/documentation/build/querying-the-knowledge-base)** | The retrieval corpus. Documents the agent searches to ground an answer. Two words, never one.                                             |
| **[Data source](/documentation/build/importing-data-sources)**         | Where knowledge base content comes from: a file, a URL, or a synced integration.                                                          |
| **[Variable](/documentation/build/data/variables)**                    | A named slot of project state an agent reads and writes during a conversation.                                                            |
| **[Secret](/documentation/build/data/secrets)**                        | A credential stored for the agent to use without exposing it in a prompt or a function.                                                   |
| **[Persona](/documentation/build/data/personas)**                      | A saved set of traits used to simulate a particular kind of user when testing.                                                            |
| **[PII redaction](/documentation/build/data/pii-redaction)**           | Stripping personal data from what gets stored.                                                                                            |
| **Document**                                                           | One source inside the knowledge base: a file, a page, or a synced record. Retrieval returns passages from documents, not whole documents. |