In this introductory chapter, various terms and concepts referring to conservative religious groups are discussed, including fundamentalism and strong religion. Arguments for the use of the term conservative religion are presented. Usually, groups of conservative religion are characterized by conservative theology and morality, while their views of social and political matters can vary. Processes of modernisation and secularisation are also discussed in this chapter and related to conservative religion in the past and present. Finally, the introductory chapter contains a presentation of the subsequent chapters. The presentation concludes in a discussion of the strategies used by the groups under study in the empirical chapters: opposition, negotiation and adaptation.