Secrets
Secrets are anything important about a character's background or story that can't be public knowledge without quite possibly changing how the character is perceived, with secrets quite often being vital to a character's nature but absolutely ruinous if they became known. For example, a character actually being a demon worshipper, or having a secret identity, or having a hidden scandal, or knowing something profoundly damaging about someone else. These don't necessarily have to be bad for a character, but should be something that has to come out in roleplay and isn't immediately accessible.
Roster character secrets can be viewed with @sheet/secrets.