Visible and invisible

There is a distinction to be drawn between the church as people see it and as God alone sees it. This difference is the historic distinction between the "visible church" and the "invisible church." "Invisible" does not mean that no part of it can be seen, but that its exact boundary is not known to us. Only God knows (2 Tim. 2:19) which members of the earthly congregations are inwardly born again, and so belong to the church as an eternal and spiritual fellowship. Jesus taught that in the organized church there would always be people who seemed to be Christians, not excluding leaders, who were nevertheless not renewed in heart and would be exposed and rejected at the Judgment (Matt. 7:15-23; 13:24-30, 36-43, 47-50; 25:1-46). There are not two churches, one visible and another hidden in heaven, but one church only, known perfectly to God and known imperfectly on earth.

The Reformation Study Bible, "The Church"