Learn in the textbookThe 7 Elements of Information Security
DefinitionConfidentiality (機密性) is the property that only people permitted to view information can see its content, and it does not leak to anyone else.
ExplanationInformation security rests on three elements, confidentiality, integrity and availability, known as CIA from their initials. Typical ways confidentiality is lost are leaks to outsiders and eavesdropping on communications. It is protected by, for example, encryption, which turns content into an unreadable form, and access control, which sets what each user may view.
AnalogyIt is like a records room that opens only to those who tap their staff ID card. The documents inside are seen by no one except those allowed in.
Memory hookConfidential is the word stamped on documents meant for internal eyes only, and it signals a limited audience. It supplies the C in CIA.