Initially, one way of identifying totalitarianism that appears rather straightforward is by listing totalitarian systems in history: the usual list would at least include Fascist Italy, Nazi Germany, the Communist regimes of the Soviet Union, the People’s Republic of China, the Democratic People’s Republic of Korea, and Democratic Kampuchea, among others. Because of the broad use of the term, it will be useful here to examine some common descriptions for totalitarianism that can confuse an understanding rather than bring clarification. One influential means of understanding totalitarianism attempts to examine it through social science. In most cases, totalitarianism develops (and has the greatest success) in periods of significant instability, be it economic, social, political, or even cultural. Totalitarian governments will often engage in, and maintain, policies that look irrational (or even borderline insane) when viewed from the outside. The chapter also presents an overview on the key concepts discussed in this book.