Together with the Epistles of James, Peter and Jude, the three Epistles of John belong to the 'general epistles'; a man-made name that does not actually do justice to these letters. The content shows that these letters are not just written to Christians in general, but to readers with a Jewish / Israelite background.
For information about the writer and the origin of the letter, see the previous section on the first letter of John. John, who was one of the "pillars" of the church in Jerusalem (Gal. 2:9), calls himself "the elder" in the second and third letter of John.
These two letters are more personal in nature than the first letter of John. Thus John writes his second letter to "the chosen woman and her children" (v. 1) and his third to "the beloved Gaius" (v.1). So they are letters that are more intended for individuals. And for both persons it is true that John loves them "in truth". And with that we actually immediately get to grips with the general theme of these letters: the truth; both the walk in the truth, and the witness that proceeds from the truth.
A. 1-3 To the elect woman and her children; praise.
B. 4-6 The walk according to the commandment of the Father.
C. 7 and 8 Deceivers.
B. 9-11 Opposition to the teachings of Christ.
A. 12-13 Children of your chosen sister; greeting.
A. 1 and 2 Salute.
B. 3 and 4 Testimony of the walk in the truth.
C. 5-8 Love to strangers is praised.
D. 9 and 10 The evil done by Diotrephes.
C. 11 Exhortation to do good.
B. 12 Testimony of the Walk in the Truth.
A. 13 and 14 Salute.
The content of the second letter of John corresponds to a large extent with the first letter of John. John also writes to the "chosen woman and her children" about abiding in the truth and walking in His commandments. There we also find the warning for the many deceivers who have gone out into the world and who, in accordance with the deceiver and the antichrist, do not confess the coming of Jesus Christ in the flesh (v. 7).
As was the case with the first letter of John, the following two letters of John are also written against the background of the very imminent coming of the Lord Jesus Christ. And in that time leading up to the revelation and presence of the Lord Jesus Christ, it is especially important to bear witness that springs from the truth. Certainly when we view the second letter of John against that background of the revelation, we might also see in the "chosen woman and her children" a picture of the woman and her progeny in the last book of John, the Revelation of Jesus Christ (cf. Rev. 12:1, 6 and 17). Revelation 12:17 says, "And the dragon was wroth with the woman, and went to make war with the rest of her seed, which keep the commandments of God, and have the testimony of Jesus...". This 'keeping the commandments of God' is again fully in line with 2 John 4-6.
All in all, the second and third letters of John are also writings that exhort the believers to walk in the truth and warn them against deception and the like.
"And this is love, that we walk after His commandments" (2 John 6a) and "Beloved, do not imitate evil, but good. He who does good is of God..." (3 John 11 ).