Catholicism is the belief and practices of the Catholic Church.
What is the purpose of the visible Catholic Church including its role on earth?
The purpose of the visibile Catholic Church is to build up the Kingdom of God, and its role on earth is to carry on the mission of Christ as priest, prophet, and king; or to put it in other words, to sanctify, evangelize, and serve.
To state this yet another way, let me quote the words of my pastor, who addressed this in a letter to our parish: “As a people called by God and formed in His image, we share in the mission of the Church which continues the mission of Jesus Christ as Priest, Prophet, and King. Each of us, by virtue of the grace received at baptism, are given the vocation to lives of holiness through the sacramental life of the Church [priest], to proclaim the Gospel in our words and deeds [prophet], and to live in justice and charity with others [king].”
How does the visible Catholic Church operate in order to attain its purpose?
Christ founded the Church on earth and established Peter as its head on earth.
(Reference Matthew 16:18 “And so I say to you, you are Peter, and upon this rock I will build my church”.)
And he gave the apostles a mission.
(Reference Matthew 28: 19-20 “Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit, teaching them to observe all that I have commanded you.”)
And the authority he gave to the apostles is handed on to successors, to continue this mission. Thus we have successors to the Peter, the Vicar of Christ (the pope) and the successors to the apostles (the bishops). And through them and our priests and deacons, we have the hierarchy of the Church which leads the flock in the building up of the Kingdom of God.
What is the Mystical Body of Christ?
The Mystical Body of Christ is all the baptized, those on earth who are Christ’s hands and feet and eyes and ears, who are Christ to one another.