Question: "What do the seven churches in Revelation stand for?"
Answer: The seven churches described in Revelation 2-3 are seven literal churches at the time that John the apostle was writing Revelation. Though they were literal churches in that time, there is also spiritual significance for churches and believers today. The first purpose of the letters was to communicate with the literal churches and meet their needs at that time. The second purpose is to reveal seven different types of individuals/churches throughout history and instruct them in God's truth.
A possible third purpose is to use the seven churches to foreshadow seven different periods in the history of the Church. The problem with this view is that each of the seven churches describes issues that could fit the Church in any time in its history. So, although there may be some truth to the seven churches representing seven eras, there is far too much speculation in this regard. Our focus should be on what message God is giving us through the seven churches. The seven churches are
(1) Ephesus (Revelation 2:1-7) - the church that had forsaken its first love (2:4).
(2) Smyrna (Revelation 2:8-11) - the church that would suffer persecution (2:10).
(3) Pergamum (Revelation 2:12-17) - the church that needed to repent (2:16).
(4) Thyatira (Revelation 2:18-29) - the church that had a false prophetess (2:20).
(5) Sardis (Revelation 3:1-6) - the church that had fallen asleep (3:2).
(6) Philadelphia (Revelation 3:7-13) - the church that had endured patiently (3:10).
(7) Laodicea (Revelation 3:14-22) - the church with the lukewarm faith (3:16).