Saint Peter was a very important person from a long time ago who believed in Jesus and helped spread his message. Some people even say that Jesus made him the leader of all the other followers. He was called a apostle because he traveled around with Jesus and learned from him. After Jesus died, Saint Peter continued to teach people about his message and started new churches.
Saint Peter is especially famous for being the one who guards the gates of heaven, which is where people go after they die if they have been good. It's said that Saint Peter will decide who gets in and who doesn't based on how they lived their life. Some people even pray to Saint Peter for help and protection.
Overall, Saint Peter is a really important person in history who helped spread the message of Jesus and is believed by some to be the protector of heaven's gates.