What do we mean when we make the distinction between the visible and invisible church? And what is the reason for this distinction? Starting around the 4th century - the expression "Visible Church" was refered to by theologians, not to a building, but to the members on the rolls of a local church. In other words, all persons who are members of a local church are considered to be a part of the visible church.
On the other hand, the invisible church refers to those persons who have actually been regenerated or quickened by the Holy Sprit, God's elect or true believers. Augustine referred to the church as a mixed body, a visible people, but this people has both tares and wheat, as described by Jesus. In other words, there is no such thing as a perfect church, and there will always people in the church there with bad motives or are there for the wrong reason. There will always be people who claim to love Christ but whose heart is far from Him. Many, Jesus says, will say on that day, did we not do this and that in your name? Jesus wil then say, "I never knew you". These are descriptions of some people now sitting in your local church and Jesus says of them that he "never knew them!!!" Some persons are in church for show, to be seen by men as pious, others perhaps for a social club or to show of their ability to wax eloquent when discussing theology. These persons hearts are completely invisible to us, but of course, they are not invisible to God and only He can know who is truly regenerate, so we must be generous in our judgements.
The following is a detailed description of the orthodox doctrine of the visible and invisible church as explained by Pastor Brian Schwertley. It is well worth reading and quite helpful: