This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book discusses that the religion is an elusive subject because of its complexity and its tendency to not readily reveal its secrets. It discusses the term religion for practical purposes, even if it has limitations in a cross-cultural context. Culture and religion are so intertwined, as the web metaphor suggests, that it can be safely asserted that there is no religion outside of culture. The metaphorical spider web thus points to creative abilities of human agents, who create cultural elements such as religion. The phenomenon of experience can be traced back to an Indo-European verbal root meaning to attempt, venture, or risk. Although "mysticism" is a Western term, there is ample evidence for its existence in a cross-cultural context. From a cross-cultural perspective, the scholar is condemned to use imperfect categories, such as religion and experience, to discuss global religious traditions.