In this chapter I first present a brief overview of the different datasets on armed conflict that are available. I then provide a preliminary typology which attempts to place various types of collective violence in context to each other (civil war, interstate war, terrorism, genocide, communal conflict, etc.). Finally, I discuss the consequences of having differing conceptual frameworks and definitions within the conflict data community. I argue that while the plethora of definitions may lead to confusion, heterogeneity amongst the different armed conflict data projects nevertheless serves as a key indicator for the validity of the statistical inferences researchers wish to draw. Without theoretical or empirical consensus regarding exactly what behavior constitutes armed conflict, the diversity of definitions and data provides a means to examine the robustness of the conclusions drawn in the quantitative study of armed conflict.