What really is the difference between the “Roman Catholic Church” and the “Catholic religion”?
The Catholic Church practices the Catholic Religion. This Church is the group of sui iuris or self-governing Churches in communion with the Pope. We treated this in a different article describing the many Churches that form the Universal Catholic Church.
These particular Churches have distinctive rites, which term refers to a liturgical, theological, and spiritual heritage. All these particular Church, though distinct in customs and rubrics, adhere to the Pope and have essentially one doctrine. So any Church that isn’t in communion with the Pope isn’t part of this Universal, Catholic Church.
The Roman Catholic Church or the Roman rite includes most of the Catholics in the Western world. A Roman Catholic is a person who is a member of the Roman rite. So, a person who is a member of the Catholic Church, but isn’t part of the Roman rite is Catholic, but not Roman Catholic. He could be Catholic, but part of the Armenian Rite.