Those who apply the term “Catholic Church” to all Christians indiscriminately find it objectionable that a term designating the whole Church (as an invisible entity) should be used to refer to one communion only. However, the Roman Catholic Church, which normally refers to itself simply as the Catholic Church, and which published a “Catechism of the Catholic Church” in 1992, can be traced historically to be, basically, the continuation of the original Catholic or universal Church, from which other groups broke away at various times in history. The Catholic Church holds that there can be no such thing as the Church as an “invisible entity” ONLY. Since the time of the Reformation in the 16th century, Protestants (those who protest) have sought to restore a more primitive expression of the Church, whose goals and beliefs they believe to be more consonant with the early Church, based primarily on Scriptural texts. However, there was a span of time exceeding a millennium between the “early Church” and the Reformation during which both Scripture and Christian teaching were maintained.
This is from Wikipedia, an online encyclopedia. Wikipedia can hardly be described as a Catholic apologetics sight, but simply an objective information source. I thought it might serve as an effective tool for any protestants out there who are having doubts as to which is the original Christian church.