What is the church of Christ?
Churches, as described in the New Testament, are made up of people. A church is not a building where people meet or an organization to join, like a club.
In the Bible, we see that churches are a collection of people who had heard the gospel (the good news about Jesus) and obeyed it to become disciples (followers) of Jesus. (Acts 14:21-23)
The Bible describes groups of these disciples as "churches" in Romans 16:16. However, these groups of disciples are not only described as churches, but as churches that are "of Christ."
Identifying themselves as "of Christ" was a way to show that they were not saved "of works," "of men," or by any other means. They were saved by Jesus Christ.
Ephesians 2:8-10 reads, "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them."