3 John is a personal letter from the apostle John to a man named Gaius. In the letter, John commends Gaius for his faithfulness and hospitality towards fellow believers who are traveling through his region. He also warns against a man named Diotrephes, who is known for hogging leadership roles and spreading slanderous accusations. John encourages Gaius and other believers to imitate good examples and to persevere in love and obedience to God. Overall, 3 John emphasizes the importance of hospitality, humility, and discernment in the Christian community.