what's a "catholic christian"?

Answer 1

All persons who recite the Creed are Catholics. They include members of the Roman, Anglican, Coptic, etc., etc., Churches and as such, are all members of the Holy Catholic Church.

Those among them who do not accept the POPE are the head of all Catholic Churches are simply Protestant Catholics.

Methodists and the like, who do not recite the Creed are simply Non-conformist Christians who have nothing to protest about since the are not members of the Holy Catholic Church