The Roman Catholic Church is the original universal Christian Church that was instituted by Jesus Christ,
"And so I say to you, you are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven." (Matt.16:18-19)
The Catholic Church is a worldwide community of believers that have been called by God to make the kingdom of God present in the world, by living out their faith and love for God and others.
The Catholic Church is the only Christian Church that has existed since the time of Jesus. There has be an unbroken succession of popes that can be traced back to Peter. For the first 1,000 years there was only the Catholic Church. The first break occurred in 1054 when the Eastern Orthodox churches broke from unity with Rome and the pope. The next break began with the Protestant Reformation in 1517. All other Christian groups are offshoots of the Catholic Church or offshoots of Christian Churches that came from the Catholic Church.
What distinguishes the Church from other churches are its four marks. The Church is one, holy, catholic and apostolic.
The Church is One: Jesus established one Church and teaches just one set of doctrines.
The Church is Holy: This does not mean that everyone in the Church is holy, but the Church is holy because it is a source of holiness, which is primarily expressed through the seven sacraments.
The Church is Catholic: The word catholic in Greek means "universal". The Church is catholic because it is for all peoples and nations. The Catholic Church follows its mission to "make disciples of all nations" (Matt. 28-19).
The Church is Apostolic: Jesus appointed the apostles as the first leaders of the Church. They were the first bishops and their successors have been faithfully handing down the teachings given to them by Christ for 2000 years.