In his first letter to the disciples in Corinth Paul explains to them what church is and he also does the same thing with the disciples in Rome. He wanted to make sure they understood who they were together and that each one of them formed the body of Christ, the Church of Christ.
Now you are the body of Christ, and each one of you is a part of it. (1 Corinthians 12:27)
For just as each of us has one body with many members, and these members do not all have the same function, For as in one body we have many members, and the members do not all have the same function, so in Christ we, though many, form one body, and each member belongs to all the others. (Romans 12:4-5)
