So, John the Evangelist is a very important person in the Christian religion. He was one of Jesus' disciples, which means he followed Jesus and learned from him.
John lived a long time ago, a very long time ago in fact, when there were no cars or phones or computers like we have today. People usually walked everywhere and talked to each other face to face.
John was special because he was really close to Jesus. He wrote down things that Jesus said and did and taught people about them. This way, people who didn't get to meet Jesus could still know about him and learn from his teachings.
A lot of people love John so much that they started calling him "the beloved disciple". This means that he was very much loved by Jesus and his followers.
Even though John lived a very long time ago, people still read his writings today to learn about Jesus and what he stood for. That's why he's still so important to Christians all over the world.