2John is tied for the shortest book, along with 3John and Jude, among the General Epistles with only one chapter. 2John is also the shortest of this group in terms of total verses (13) and the second smallest in terms of words (298) based on the KJV translation.
Date Written, Location
The book of 2John was written by John the Apostle between 63 and 64 A.D. He likely wrote the book from Ephesus.
[When Was the New Testament Written?]
The Author
John, in late October 26 A.D., was one of the first two disciples called by Jesus (John 1). John, along with his brother James and father Zebedee, as well as Andrew and Peter, operated a fishing business on the Sea of Galilee before their calling (Luke 5:10). This business was likely fairly prosperous as Zebedee was able to afford hired servants (Mark 1:20).
John wrote five New Testament books during his ministry. He likely died around 100 A.D. shortly after canonizing the New Testament. His grave is believed to be in Ephesus.
[Why Do Fish Symbolize Christians?]

2John Chapter Outline
Chpt. 1: The Apostle John opens his letter by greeting an unknown Christian woman and her children. Where the lady lived is unknown although commentaries have speculated she may have resided near Ephesus.
John informs the woman that she is known and loved by others for her belief in and practice of the truth. He then offers the unique blessing of grace, mercy and peace from the Godhead in truth and love (2John 1:3).
John then states his joy in finding her children are also walking in the truth, meaning that they make obedience to God a part of their daily life.
[What Does It Mean to Walk with God?]
The apostle in 2John then reveals that in order to love God we must center our lives on obeying His commandments.
As we obey the commandments, both in the letter and their spiritual intent, we grow toward fulfilling their intent which is the love of God (Matthew 22:36 - 38). Such obedience also leads us to love others, especially those who are Christians (1John 5:2).
"Christian love is not an emotion that we work up; it is simple obedience to the Word of God. Children love their parents by obeying them." (Wiersbe Expository Outlines).
The apostle then warns in verse 7 of 2John of a damnable heresy called Docetism which denies that Jesus manifested himself on earth as a flesh and blood human. John makes it clear that those who teach this false doctrine are not true believers and do not represent the truth. They are, instead, antichrists meaning that they are enemies of God who seek to deceive.

The symbolism of John holding a chalice with a serpent is based on a legend. The legend states that after he was handed a cup of poisoned wine he blessed it, causing the poison to rise in the shape of a serpent. |
John then exhorts his readers to test those who say they are Christian teachers and if they are found wanting to not even which them well or godspeed!
[What Are the Bible's Basic Teachings?]
2John closes with the apostle stating he hoped to make a personal visit and sent greetings from the Christian woman's sister and her children.