The book of Revelation is written by:
John to the seven churches which are in Asia, (1:4) to Ephesus, Smyrna, Pergamos, Thyatira, Sardis, Philadelphia, and Laodicea. (1:12)
John saw seven golden candlesticks, and in the middle of the candlesticks was Jesus… In his right hand he held seven stars, from his mouth came a sharp two-edged sword…(1:12-16)
…the seven stars are the angels of the seven churches, and the seven candlesticks are the seven churches. (1:20)
…the sword of the Spirit, which is the word of God (Ephesians 6:17)
For the word of God is quick, and powerful, and sharper than any two-edged sword… (Hebrews 4:12)
In chapters 2-3, individual letters are written to each of the churches. Each letter begins with a description of Jesus and ends with a promise to those who overcome.
Each includes a combination of these: attributes, shortcomings, warnings, consequences and instructions.
Jesus listed no shortcoming for two churches: Smyrna and Philadelphia
Jesus listed no attributes for one church: Laodicea
The seven churches existed at the time John wrote Revelation. Some believe the seven churches are also a picture of the progression of the church through history and the church of the Laodiceans represents the condition of the church today.