Every religion has its important figures. Buddhism, of course, has Buddha, and Islam has the prophet Muhammad. At the center of Christianity is Jesus Christ, who all Christians worship. But there are other important figures in Christianity. Some of these people are called apostles.
Most of the apostles lived in Jesus's time. They were close followers of Jesus. They traveled with him just about wherever he went. Jesus chose his apostles - before traveling with Jesus, they all had usual jobs. Some were fishermen; one was a tax collector. But once they were selected by Jesus, they became apostles. And to many Christians, they became saints, or holy figures.
Two of these apostles were Peter and Paul. Peter was one of the closest apostles to Jesus. Peter taught many people about Jesus. He was with Jesus on the night Jesus was betrayed. According to the Christian holy book, the Bible, Jesus said that Peter would deny knowing him. Peter said that he wouldn't, but Jesus said that before a rooster crowed, Peter would deny him. Before Jesus was taken into custody by the authorities, a crowd of people surrounded Peter. They said they remembered seeing him with Jesus. As Jesus said, Peter denied knowing Jesus. According to the Bible, the rooster crowed, and Peter remembered Jesus's words.