Scholarly efforts to understand conspiracy theories have grown significantly in recent years, and there is now a broad and interdisciplinary literature. In reviewing this body of work, we ask three specific questions. First, what factors are associated with conspiracy beliefs? Our review of the literature shows that conspiracy beliefs result from a range of psychological, political, and social factors. Next, how are conspiracy theories communicated? Here, we explain how conspiracy theories are shared among individuals and spread through traditional and social media platforms. Next, what are the societal risks and rewards associated with conspiracy theories? By focusing on politics and science, we argue that conspiracy theories do more harm than good. We conclude by suggesting several promising avenues for future research.