Simplify the following text for a Grade 9 native English-speaking person.
Original: For many hundreds of years , the Roman Catholic Church has regarded itself as the only Christian Church and has called itself the Catholic ( or `` universal '' ) church . In other words , only those people who were within the organization of the Roman Catholic Church were believed to belong to the Universal Church .
Simplified: Like the Roman Catholic Church , the Orthodox Church and some others have always referred to themselves as the Catholic church .