Okay, so there was a guy named Paul who lived a long time ago, like even before your great-great-grandparents were born. He wrote a lot of letters to people who followed a man named Jesus, who was like a really important and special person to them. These people were called Christians.
Paul used to not like these Christians at first because he thought they were wrong and bad. He used to even hurt them and make them go to jail! But then one day, he had a special moment where he saw Jesus and realized that he was wrong. From then on, Paul wanted to help the Christians instead of hurting them.
He traveled to many different places to teach people about Jesus and to help them understand what Jesus wanted them to do. Even when people were mean to him or tried to hurt him, he kept going and told them about Jesus anyway.
Later, after Paul died, people remembered him as a really important person who helped the Christians understand Jesus' message better. They think that his letters to them are some of the most important parts of their holy book, called the Bible. And that's why we still talk about him and study his writings today!