For a long time, populism was perceived as a political and social fringe phenomenon. However, this supposed marginal phenomenon is increasingly encroaching on the center of society. For some political actors and observers, this leads to a feeling of insecurity, while others nurture hopes for change. Populism politicizes and shakes old certainties, creating a need for orientation. By introducing the most important theories on populism, this volume provides answers to central questions that have come to the forefront in public discourse and academia in light of populism: What is populism and under what conditions does it arise? How should populism be assessed, and what does its current rise signify?.