What is a counterrevolution? And how often do they occur? Chapter 2 is devoted to answering these foundational questions. According to this book, a counterrevolution is an irregular effort in the aftermath of a successful revolution to restore a version of the pre-revolutionary political regime. The chapter begins by explaining and contextualizing this definition. It reviews the various alternative understandings of counterrevolution that have been invoked by both scholars and activists. It then explains the decision to adopt a definition of counterrevolution as restoration and shows how this definition was operationalized in building the original dataset. The second half of the chapter lays out the main high-level findings from this dataset. About half of all revolutionary governments have faced a counterrevolutionary challenge of some type, and roughly one in five of these governments was successfully overturned. Moreover, these counterrevolutions have been distributed unevenly: the vast majority have toppled democratic revolutions, rather than ethnic or leftist ones. And counterrevolutions had for years been declining in frequency, until the last decade when this trend reversed. These descriptive findings provide the motivation for the theory developed in Chapter 3.