[11] John doesn't want the other believers to follow Diotrephes bad example. He reminds them that, "...those who do good prove that they are God's children and those who do evil prove that they do not know God."
[12] John is impressed with what he's hearing about Demetrius. It seems that everyone that knows Demetrius, speaks well of him. Demetrius is a convert from paganism (as we all are). He is sound in the faith and in truth. He is genuine, dependable and humble in his everyday walk. This is the only scripture that mentions Demetrius in the Bible. It shows that God uses individuals, in even the smallest of ways. Demetrius isn't doing anything "spectacular" for Jesus. He lives day-to-day for God. He is probably un-noticed by the world, but God draws special attention to his faithful life.
[13-14] John wants to tell them more - but not through letters. He wants to talk face to face.
[15] John wishes Gaius peace & sends greetings from other believers in Jesus. He wants Gaius to tell his friends, "hello".
