An epistle is a writing or letter directed or sent to a person or group of persons. The vast majority of the New Testament is comprised of epistles. Some of these letters were sent to individuals (Philemon, 1 Timothy, 2 Timothy, Titus, 3 John), some to churches (Romans - 2 Thessalonians) or other groups (Hebrews - Jude). The Book of Revelation was not sent to a single church, but rather to a group of churches, as was 1 Peter and possibly 2 Peter.