Defining "Church" was one of the most controversial topics during the time of the Lutheran Reformation.

Properly speaking, the church is the assembly of saints and true believers.

The Church is primarily the gathering of God's people around Christ's Word and the Sacraments of Holy Baptism and the Lord's Supper. In the wide sense, the visible church includes all who are seen to gather around the Sacred Word of God and the Sacraments. This, of course, includes hypocrites and evil persons who mingle with believers, including some pastors and leaders of the church organization.

In the narrow sense, the invisible church includes all who genuinely have faith in Christ, an aspect of the Church that cannot be seen. Fellowship around, in, and through the Word and Sacraments define unity in the faith.

The apostle Paul writes regarding Christ's work in the making of the saints of the Church, by grace alone in his letter to the saints, the faithful believers in Christ of the Church at Ephesus: Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word, so that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish. [Ephesians 5:25b–27]