Totalitarianism is a political system where the government exerts total control over all aspects of life, characterized by an all-powerful leader and systematic use of terror and violence. Key features include a cult of the leader, radical ideology, mass mobilization, indoctrination, and the suppression of dissent through secret police. Historical examples include Benito Mussolini's fascist regime in Italy, Joseph Stalin's communist state in the Soviet Union, and Adolf Hitler's Nazi Germany, each using their own methods to maintain control and promote their ideologies.