In this letter, the key issue seems to be that some are teaching that Jesus was never human, but only God. (This teaching has been rejected historically by the church which believes that Jesus was "fully human, fully divine" -- completely God and human being at the same time.) The church must avoid such teachers, and focus only on the example and commandment of Jesus to love one another.
[links to Bible Gateway open in a new window]Reading the Bible in Its Entirety
If you are planning to read the Bible in its entirety, you should read 2 John 1 today.