I am not sure the FR Religion Forum is strictly governed by Canon Law (!) ("That's a joke, son") but I am using that as an illustration that the term "Catholic" --- like most words --- can cover several, slightly differing semantic fields.
You'll never quite grasp this until you distinguish the range of recognized usages.
Context is your friend.
Dictionaries help, too.
Catholic to you means the Roman Catholic Church.
To Christians it means the universal church of those who follow Christ.
Again, in debating with Roman Catholics a set of agreed upon definitions is required as Rome likes to redefine common words to sometimes mean other than what they are.