Okay kiddo, today we're going to talk about a type of religion called "old Catholicism". It's a bit different from other types of Christianity, so we'll break it down step by step.
First of all, Catholics are people who follow the teachings of Jesus Christ as taught by the Roman Catholic Church. But old Catholics are people who used to follow the Roman Catholic Church, but now have a slightly different way of doing things.
See, a long time ago, there was a big argument between the Pope (who is the leader of the Roman Catholic Church) and some other Christians. This argument was called the "First Vatican Council," and it happened in the late 1800s.
During this argument, the Pope said that he had more power and authority than anyone else in the Church, and that everyone had to do what he said. But some people didn't agree with him. They thought that everyone in the Church should have a say, and that the Pope shouldn't have so much power.
So these people decided to start their own Church, which became known as "Old Catholicism." They still believed in Jesus and the Bible, but they didn't agree with how the Pope was running things.
One of the main things that old Catholics do differently is that they don't believe in the idea of "infallibility." This means that they don't think that the Pope (or anyone else) is always right and can never make mistakes.
So that's it in a nutshell, kiddo. Old Catholics are people who used to be part of the Roman Catholic Church, but now have their own Church because they don't agree with some of the things the Pope says and does. They still believe in Jesus and the Bible, but they have their own way of doing things.