A set of data describing the DID subject, including mechanisms, such as cryptographic public keys, that the DID subject or a DID delegate can use to authenticate itself and prove its association with the DID. A DID document might have one or more different representations as defined in 6. Representations or in the W3C DID Specification Registries [DID-SPEC-REGISTRIES].
Relevant properties: https://www.w3.org/TR/did-core/#did-document-metadata