The aim of this book is to show what religion is, what religion consists of, and how religion works. To this end, we start by formulating a general definition of religion. Then we give a general description based on the literature of the history of religion. This is followed by a chapter in which we critically discuss the existing research in broad outline and discuss the major theories about religion. In chapter three we formulate a general theory about religion using existing theories. The fourth chapter explains how religion comes into being. Finally, the fifth chapter focuses on explaining religious events. This book is written as an introduction to the study of religions from a scientific and therefore non-religious perspective. It is suitable for people who respect religion and who want to know why people behave the way they do under the influence of religion. It is a book for people who realize that religion as a universal human cultural expression has always been, is and will remain an active factor in the psychological, social and cultural life of humanity.