Religion and spirituality seem to be distinct ‘entities’. One can point to a church, and assume that one can find ‘religion’ there. One can point to a meditation centre, and assume that at least some people there will be calling themselves ‘spiritual’. One can point to certain behaviours and practices, and identify those as religious. This chapter conceptualizes spirituality as a category and as a domain of practice, before going into the theme of gender and how this is linked to the differentiation between public and private domains, secular and religious domains. So when did ‘spirituality’ emerge as something that can be distinguished from religion and the secular? According to van der Veer, the category of spirituality emerged during the nineteenth-century Great Transformation, when the world became integrated in terms of economics, politics and culture. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book.