History can be described as the organised memory of the humankind. Different literal, oral, and material remains of the past - called sources - form the content of this memory.

Church history is part of both history and theology. History, including church history, is being studied in order to maintain a sense of continuity. Without the sense of tradition carrried on for generations one is not capable of understanding the literal sources of Christianity like the Bible, the Creeds or for example journalism within the church.

Church history is closely connected to other research of history and other fields of social science and arts. Society as a whole, affected by churches, religious groups and their opponents, forms the actual field of study for church history. Church History as discipline in the Faculty of Theology of the University of Helsinki consists of two subjects: General Church History and Finnish and Scandinavian Church History.