An SSL Certificate associates an entity (person, organization, host, etc.) with a Public Key. In an SSL connection, the client authenticates the remote server using the server's Certificate and extracts the Public Key in the Certificate to establish the secure connection. The authentication is done by verifying that the public key in the certificate is signed by a trusted third-party Certificate Authority.
If a client is unable to verify the certificate, it can abort communication or prompt the user to continue the communication without authentication.
But how this can be true when we are performing scan on IP