Default macOS certificates not trusted and not verified by third party

When I start a new Mac OS system from scratch, inside the keychain application I notice there are 3 certificates that are not trusted or not verified yet. I know I can double click each one of them and make them trusted for the entire system. But my question is what are those certificates for? What is the purpose of these certificates and should I make them trusted? or not? One certificate is located inside the Keychain under the Login section: **member: xxxxx-xxxxx-xxxx-xxxx-xxxxxx** (expire in one year from the current date) (this certificate has not been verified by a third party) The other 2 certificates are located inside the Keychain under the System section: **com.apple.kerberos.kdc** and **com.apple.systemdefault** (expires in 2040) (this certificate has not been verified by a third party.)