As is well known, the book of Revelation is often termed "the Apocalypse," and is rightly so called when we realize that this is simply a brief way of referring to the Apocalypse of John. "Apocalypse" (which derives from the Greek word "Apokalupsis" —meaning "revelation") was a name given to a specific type of literature consisting largely of the visions of the narrator. Thus in the Old Testament, the book of Daniel is essentially apocalyptic in form, and is in many respects similar to the book of Revelation. Both writers made it their aim to encourage their countrymen in times of severe religious persecution.
When the book of Daniel was written, the Greeks, led by Antiochus IV, were seeking to exterminate Hebrew religion, and the author reminded the Jews of the signal deliverances wrought for men of their nation even in pagan Babylon. In the days of John, the Roman Emperor Domitian was endeavoring to stamp out Christianity, and the apostle brought to his fellow Christians encouragement and cheer. John had himself felt the lash of persecution, for it was evidently during his exile on the island of Patmos that he set down his inspiring message (Rev. 1:9). To John, this book was a revelation indeed, granted to him by the Founder of Christianity, for he terms it "the Revelation of Jesus Christ, which God gave unto him," and says that "he sent and signified it by his angel unto his servant John" (Rev. 1:1). It is not surprising that it differs not a little in style as well as in content from the Gospel and three epistles which are also attributed to the "disciple ... whom he loved."
The book of Revelation purports to be written primarily for the benefit of a group of seven Christian churches situated in the western section of Asia Minor, but John's message is by no means limited to that district or to the closing years of the first century, when it was recorded. With clear insight the writer singles out the virtues and the faults of each community, beginning very naturally with Ephesus, where he appears to have spent much of his latter years; and interspersed with his words of warning and of praise we find reminders of the rewards of steadfastness in time of persecution.