Essentially The Revelation Is a Book of Symbols.

The Seven Churches of Revelation, also known as The Seven Churches of the Apocalypse and The Seven Churches of Asia (referring to the Roman province of Asia, not the entire continent), are seven major churches of Early Christianity, as mentioned in the New Testament Book of Revelation.

We continue with our study of the Apocalypse or Revelation of John (the Apostle), written from the Greek island of Patmos in the Aegean Sea, off the coast of modern Turkey. John writes to

... the seven churches that are in Asia: Grace to you and peace from him who is and who was and who is to come, and from the seven spirits who are before his throne, and from Jesus Christ the faithful witness, the firstborn of the dead, and the ruler of kings on earth. To him who loves us and has freed us from our sins by his blood and made us a kingdom, priests to his God and Father, to him be glory and dominion forever and ever. Amen. - Rev 1:4-6 ESV

"Churches" in this context refers to the community or local congregations of Christians living in each city, and not merely to the building or buildings in which they gathered for worship. In fact, church buildings would not appear to any extent, until a couple hundred years later. John is instructed to write to seven of those Christian communities. There may well have been more. Seven here must be interpreted as a symbol for all churches.  Seven is an important symbolical number in the Bible denoting completion. Some examples:

• Gen. 1:31 - 2:3 - God completed His creation in six days and set the seventh day aside to rest. Thus seven became the number for completion. It still marks the completion of our week of days. 

• In Rev. 13:18 "the number of the beast" is called "the number of a man": 666. Man was created on the 6th day. If God's number is 7, then man's is 6, indicating clearly that man is not God. He was created by God on day 6. The number of man is written 3 times. The number 3, as we'll later learn, is also God's number, the number for the Trinity. In claiming 666 we will learn that the beast is claiming to be God and worthy of worship.  

• Series of sevens often appear in the Bible. So we find:

• Gen. 7:2 - 7 pairs of each clean animal enter the ark. 
• Exodus 25:37 - the Menorah, the tabernacle's lamp stand, has 7 stems
• Proverbs 6:16-19 - The LORD hates haughty eyes, a lying tongue, shedding of innocent blood, a heart devising wicked plans, feet that run to evil, a false witness and one who sows discord.
• Matt. 18:22 - wrongdoers are to be forgiven 70 X 7. 
• In the Revelation the number 7 is used more than 50 times. e.g. 7 letters to 7 churches in Asia and 7 spirits before God’s throne (Revelation 1:4), 7 golden lamp stands (Rev.1:12), 7 stars in Christ’s right hand (Rev. 1:16), 7 seals of God’s judgment (Rev. 5:1), 7 angels with 7 trumpets (Rev. 8:2), etc. 

So here in the beginning of The Revelation the number 7  represents completeness or totality: the 7 churches represent the completeness of the body of Christ, the 7 seals on the scroll represent the fulness of God’s punishment of a sinful earth, and so on.

Symbolical language is very important in the Bible. One study tells us that there are 1,670 symbols in the Bible. These include the rainbow (Gen. 9:13; Rev. 4:3), thunder, lightning, cloud and smoke (Rev. 4:5; 8:5; 11:19), trumpets (Exod. 19:19; Rev. 8:6), throne (Isa. 6:1; Rev. 4:2; 22:3), white hair (Dan. 7:9; Rev. 1:14), etc. Amazing Discoveries has created a Bible Symbols Chart that you may find helpful.

By the way, what do you think about when you see men like myself with white hair ? White is the symbol for purity (Rev. 12:9; 20:2) and for victory (Rev. 19:8; 3:5; 7:14). White hair in particular is apparently a symbol for experience and the consequent wisdom that comes from the same (Rev. 1:14). We are commanded to honor the old man with gray or white hair and consider it to be a crown of glory, glory gained by living a godly or righteous life (Prov.16:31). Obviously not all of us white-hairs have earned such honor, but many have, by God's grace.

What precisely is a symbol or symbolic speech? Webster's dictionary defines it this way: A form of speech that expresses an idea or emotion without use of words. A symbol represents or suggests something abstract, such as burning one’s draft card, bra, or flag, or picketing. So throughout the Revelation we will encounter symbolic speech and we must consequently be very careful never to interpret symbols literally. An obvious example of this is the number 144,000 (12x12x10x10x10). We'll want to explore that peculiar symbolical number later. But is it only symbolical?

The problem is how to decide if one should ever interpret the symbols of Revelation as literal rather than symbolical, pointing beyond the image to an abstract concept, like 144,000 (Rev. 7:1-4; 14:1-3). Jehovah's Witnesses, for instance, claim that 144,000 is the literal number of those who will reside in heaven. The rest will live forever on earth or be annihilated. We'll come back to interpreting that symbolical number later. For the moment I believe we need some guidance on principles of interpretation (sometimes called hermeneutics).

One basic hermeneutical rule is that Scripture interprets Scripture. So right at the start we read that the Revelation comes from God to Jesus. Jesus, in turn, is to show his servants what must happen soon . To do that our Lord sent his angel / messenger to signify or make known what must happen through symbols.

The Revelation of Jesus Christ, which God gave Him to show His servants—things which must shortly take place. And He sent and signified it by His angel to His servant John, - Rev 1:1 NKJV

The Greek word for signify here is sēmainō, a favorite verb used by John in his Gospel. So Jesus spoke about his being lifted up as the means by which he would draw all people to himself. John then writes, "He said this to show (or signify) by what kind of death he was going to die. - John 12:33 ESV. The snake lifted up on a pole was a sign of what would happen when Jesus was lifted up on a Roman cross. In its noun form that word is translated simply as sign. So when Jesus heals the son of an  official from Judea John calls it "the second sign that Jesus did when he had come from Judea to Galilee" (John 4:54). The healing was a sign pointing to Jesus as the Messiah.

So we hear from the outset that this is a book of signs or symbols that show us what must happen. Essentially the Revelation is a book of symbols. That is the primary way by which Jesus chose to communicate to us through His angel. If we are to interpret these symbols in some kind of literal manner, the Holy Spirit will make that clear as well. Otherwise we'll have to treat the various images as symbols or signs, not to be taken literally. If you'd like to read more about this process of interpretation or hermeneutics, read Roy Harrisville's article "A Primer on Lutheran Hermeneutics."