What is Catholicism?

The Catholic Church, in short, is the Church that Jesus founded while He was on earth. In the Gospel of Matthew, Jesus establishes Peter as the first Pope:

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.
- Matt. 16:18

From this moment in history, the Catholic Church has maintained an unbroken line of Popes; those men who succeeded Peter in the ministry of leading the Church. By the grace of the Holy Spirit and in the name of Jesus Christ, the Catholic Church has been founding parishes, hospitals, universites, and charities all over the world.