The short letter of Second John is address to the “elect lady and her children.” This is likely a reference to a church. Since the Greek word for church is feminine, calling a church a “chosen lady” is a natural metaphor. Jobes points out that neither “chosen” nor “lady” were used as proper names in the first century, nor are there any personal names in this letter (Letters to the Churches, 441). John refers to the members of a congregation as “children” in 1 John several times, so it seems fairly certain that this address is to a congregation of believers.
It may be a generic letter, however, circulated to several churches in a region. 1 John seems to be intended as a circular letter, so it is possible that this short note from “the elder” was passed around to several house churches. Since this letter is written on a single scrap of paper (verse 12), it may have been intended as a personal note from John, carried by a traveling preacher visiting congregations under John’s oversight. Obviously 1 and 2 John are related, but there is no way to know which letter came first or if they were addressed to different congregations.
The theological content of the letter is similar to that of 1 John. The writer warns the congregation about “deceivers” who have gone out into the world and deny that Jesus came in the flesh (v. 7). In verse 9 John implies that these deceivers have “gone ahead” rather than remained in the truth as it was first taught. Perhaps some teachers had tried to find a way to explain who Jesus was which “went beyond” what the apostles originally taught.
This is a problem for modern theology. The main issue in Second John is that the false teachers had developed doctrine in a way which was unacceptable. I think they had good intentions – they were genuinely trying to explain a very difficult concept (God became flesh) and they did so in a way which they thought was consistent with their Jewish world view. But from the perspective of John, they have gone too far and need to “remain” in the original teaching he delivered to them.
I think that it is necessary to develop doctrine “beyond the Bible,” since the Bible simply does not specifically address every situation which may arise in a modern context. I am frequently asked what the Bible has to say about birth control or in vitro fertilization. Since it is very hard to “quote a verse” as a proof-text either for or against these practices, Christians have to infer ethical practice from the general teaching of the Bible. The difficult part is knowing when we have “run ahead” and developed a doctrine beyond what the intent of the Bible was in the first place.