Okay kiddo, so Paul the Apostle was an important figure in the early Christian religion. He was originally a Jewish man, but he became a Christian after he had a vision of Jesus.
Now, when Christianity started, most of the people who followed it were Jewish. They still followed some of the Jewish rules and customs, even though they believed in Jesus as their savior. We call them Jewish Christians.
Paul realized that not everyone could become Jewish before becoming a Christian, and that it wasn't necessary to follow all the Jewish customs to be a good Christian. He believed that believing in Jesus was enough.
Some Jewish Christians didn't like this idea and thought that everyone should still follow all the Jewish customs. They thought that following these customs made them better Christians.
So, Paul and these Jewish Christians had some disagreements about what it meant to be a good Christian. But ultimately, Paul's ideas became more popular and the Christian religion became more inclusive of people from different backgrounds.