St. Paul describes the Church as a body. Bodies have many members, or many different parts, that make up the whole (see 1 Corinthians 12:14-18). Without the veins, the heart cannot function. Without the blood, neither the heart nor the veins can function. And without the heart, the whole body cannot live. In a similar way, the Church is comprised of many members, all of whom fulfill their different roles (see 1 Corinthians 12:28-30). The Pope is the visible head, the bishops and the priests are ministers, the consecrated and religious men and women serve the Church through vows of poverty, chastity, and obedience, and the laity fulfill their own mission while pursuing temporal affairs.
The Catholic Church is described as having four essential features: one, holy, catholic, and apostolic. What are these four essential features, and what do they mean?
One: The Church is one because her founder is Christ himself: "There is one body and one Spirit, just as you were called to the one hope that belongs to your call, one Lord, one faith, one baptism, one God and Father of us all, who is above all and through all and in all" (Ephesians 4:5). In Christ, we are united by the bonds of unity: our profession of one faith, our common celebration of worship, and apostolic succession (see below for more information) (CCC, art. 815).
Holy: Because Christ alone is all-holy, and Christ is the head of the Church, the Church is therefore also holy. The Second Vatican Council document Lumen Gentium explains this idea well: "The Church on earth is endowed already with a sanctity that is real though imperfect" (art. 48). The Church here on earth is pilgrimaging toward heaven, where she will be made perfect. Therefore, while the Church possesses sanctity here on earth, for she has Christ as her head, she is still on a journey toward perfect sanctity, which will be found in Heaven.
Catholic: The word "catholic" means "universal" (see CCC, art. 830). The Church is universal in two ways. First, Christ is her head, such that his presence also indicates the presence of the Church. Second, the Church is universal in that she is meant to preach the Gospel to all nations: "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Hoy Spirit" (Matthew 28:19). Christ gave the universal command that all the members of his Body are meant to spread his Gospel throughout the world. Through her internal and external works, the Church reveals to the world the Gospel of Christ, which means that the Church reveals the new law of love.
Apostolic: The Church is apostolic because of the apostles. We can say she is apostolic in three ways: she remains built on the foundation of the apostles through apostolic succession; through the Holy Spirit, she continues to pass on the faith; and she continue to be sanctified through the successors to the apostles, namely, the priests, the college of bishops, and the Pope as her head (see CCC, art. 857).
The beliefs of the Catholic Church can be summarized in the Creed, but the Apostles' Creed and the Nicene Creed; we pray the Apostles' Creed at every Catholic Mass, professing the articles, or statements, of our faith that we professed at baptism. While not everything taught by the Church is mentioned in the Creed, everything we believe can be derived from its statements.
I believe in God, the Father Almighty, creator of heaven and earth.
I believe in Jesus Christ, his only Son, our Lord.
He was conceived by the Holy Spirit and born of the Virgin Mary.
He suffered under Pontius Pilate, was crucified, died, and was buried.
He descended into hell.
On the third day he rose again.
He ascended into heaven, and is seated at the right hand of the Father. He will come to judge the living and the dead.
I believe in the Holy Spirit, the holy catholic Church, the communion of the saints, the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.