Digital certificate
A digital certificate is a signed data structure that binds a public key to information about a subject, such as a person, organization, or system.
The certificate and private key are different things
A certificate contains a public key and signed information about it. In an X.509 certificate, that information includes the issuer, subject information, and validity period, with extensions describing uses and constraints.
The corresponding private key is separate. When an application authenticates using a certificate credential, possession of the public certificate alone is not enough to generate the required signature. Microsoft’s application-authentication documentation describes signing a client assertion with the private key.
This distinction matters during support work. Sharing a public certificate is different from handing over a file that also contains its private key. The application credential guide explains why the approval should identify the access a credential enables.
Valid for which purpose, and trusted by whom?
A recognizable subject name or an unexpired date does not settle whether a certificate should be accepted. The receiving system needs to apply its validation rules, including the relevant trust information and intended use.
A valid certificate also does not approve a business request. It can support authentication without establishing that the authenticated party should receive your data or change your device.
For a certificate delivered inside an Apple profile, ask what trust the installation is intended to establish. The configuration profile guide distinguishes the settings package, certificate trust, and device-management enrollment.