What is the nature of the New Testament letters?

While the New Testament epistles frequently address very specific issues, in the broadest sense their purpose is to aid believers in making practical application of the teachings of Jesus. They offer explanation, verify doctrine, answer questions, correct errors, and give cautions and encouragement. As Paul writes in 2 Timothy 3:16, 17: All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work.[NKJV]