For the first 1,500 years of Christianity there was no “Catholicism” per se because there were no other forms of Christianity to distinguish it. There was only the One, Holy, Catholic, and Apostolic Church. The word Catholic means universal. The Church was meant for all peoples at all times. The early Church understood itself as a body of believers all over the Western world united by common traditions, beliefs, church structures, and worship. Before the Reformation in the 1500 hundreds, if you were Christian, you belonged to the Catholic Church. Any other form of Christianity was considered heresy and definitely not a denomination of the Christian Church.
Today, there are many popular forms of Christianity besides Roman Catholicism. Although the Catholic Church continues to teach that it alone has carried on the true tradition of the apostolic church, the Second Vatican Council declared all baptized Christians to be “… in a certain way, although imperfect, in communion with the Catholic Church.” So, to be a Catholic today means to be a certain kind of Christian who has definite beliefs, exercises certain practices and traditions that differs itself from Protestantism, Anglicanism, Greek Orthodox, and other branches of modern Christianity.
Roman Catholicism is by far the largest Christian group of worshippers in the world. With more than one billion followers, Catholics constitute slightly over half of the world’s Christians. Catholicism is the main religion of Italy, Spain, and nearly all Latin American countries. Catholicism and Christianity are also rapidly gaining many adherents in the continent of Africa. In 2001, about 24 percent of Americans identified themselves as Catholic, making Catholicism the largest denomination in America. That statement is only true if you do not lump all the Protestants denominations together. The next largest denomination in America is the Baptists who are roughly 16 percent of the American population. Yet, if Protestants are considered as one group, Catholics remain a minority among American Christians.
Distinctive Roman Catholic beliefs include the special authority to the Supreme Pontiff, who is the current pope who occupies the Vatican, in Vatican City; the ability of saints to intercede on behalf of believers; the concept of purgatory as a place of afterlife where an individual can be purified in order to enter heaven; and the doctrine of transubstantiation, which is the changing in its essence of the bread and wine during the Eucharist into the true body and blood of Jesus Christ.
Generally, Catholic worship tends to be more formal and ritualized than its Protestant counterparts. Services follow a prescribed liturgy and priest wears more elaborate vestments than most Protestant ministers. Catholics usually celebrate the Eucharist more often than the Protestants. As part of the Catholic club rules, a Catholic is asked to attend the Eucharist on Sundays and Holy Days of Obligation. Regarding this rule, a great many Catholics may act more like they are Protestant than Catholic.