In this case, the certificate has been "self-signed", meaning that the certificate was issued by the subject itself, not ...

In this case, the certificate has been "self-signed", meaning that the certificate was issued by the subject itself, not by a well-known "certification authority".  You can authenticate a self-signed certificate only by directly verifying its digital fingerprint (a.k.a. "thumbprint"), as publicly advertised by the certificate's subject.