Q. 1. What is the difference between the words "Catholic" and "Christian?" Are all Catholics Christians? And are all Christians Catholics?
A. 1. Nowadays, we would say that Catholics are Christians, but not all Christians are Catholics. Allow me to explains.
As stated in the Holy Bible, the word "Christian" was first used in Antioch. "So it was that for an entire year they met with the Church and taught a great many people and it was in Antioch that the disciples were first called,'Christians.'" [Acts 11:26] In those days, the word "Christian represented all the "Catholics" (meaning universal faithful). Accordingly, in the days of the Apostles, all Catholics were Christians and all Christians were Catholics. There was no diffence between the two words. They were synonym of each other.
In those days, if a person did not practice the Catholic faith, meaning he did not preach it and defend it over and above being actively involved on a weekly basis, then he was neither a Catholic, nor a Christian.
Then came the Eastern Schism in 1054, this followed by division in the Christian community, starting with the 16th century Protestant Reformation. As of 1054 A.D., the meaning of the word "Christian" came to mean "those who believe in Christ." Today, there are 30,000 different religions that claim to be "Christians," some alleging as much as also being "Catholic" in the sense that they are "universal." They do this to confuse the faithful and to try and pass themselves as Roman Catholics under the Pope and the Vatican. While all the separated brothers and sisters can claim to be "Christians" because they believe in Christ, they are not "Catholics" as defined "those who are loyal to the Pope and the Vatican." Their usage of the word catholic simply means they are universal. (It should be noted that while many use the word "Catholic" to mean "universal," they are not universal. They may only belong to 1, 2 or 3 countries. As such, their usage of the word "universal" is deceiving.
Having explained why all Christians are not Catholics, it is now necessary to explain that not all Catholics are Christians. He who claims to be Catholic, but does not practice his faith, nor preach it, nor defend it, he is neither a Catholic or a Christian. He may have been baptized in the Catholic faith. But when he stopped practicing his faith, he abandonned it. He no longer belongs to it. As such, he can no longer call himself a Catholic. He is a Catholic by name only, not by association!