“Traditional Catholics” usually refers to members of the Latin church who prefer the customs and disciplines of the Latin church before Vatican II. Eastern Catholics are members of one of the nearly two dozen Eastern churches that are in communion with the Holy See (e.g., Byzantine, Maronite, Chaldean).
Eastern Catholics are, by definition, in union with the Church. Those Eastern Christians who are not in union with the Church are members of one of the various Orthodox Christian churches separated from the Holy See. Whether Traditional Latin Catholics are in communion with the Church depends on whether they attend liturgies offered by Traditionalist groups that maintain communion with the Holy See (e.g., FSSP).
