In Matthew 16, Jesus is talking to his friends, who are also called the disciples. He asks them who people think he is, and they give him many different answers. Then he asks them who they think he is, and Peter says that he believes Jesus is the Messiah, or the chosen one from God.
Jesus is very happy about Peter's answer and says that he will build his church on Peter, who he also calls "The Rock." This means that Peter will be the leader of the church and will teach people about Jesus' teachings.
Then, Jesus tells his friends that he will have to suffer and die soon, and this makes them very sad. But Jesus promises that he will come back to life after three days, and this gives them hope.
Overall, Matthew 16 teaches us that Jesus is the Messiah and that he is the one who can save us. It also shows us that even though Jesus had to go through a lot of hard things, he never gave up and gave us hope for eternal life.