Borders matter. Even in today's post-Cold War world of growing democracy, interdependence, and globalization, borders still serve a wide variety of functions across the areas of security, economics, politics, and social interactions. Despite contemporary challenges to sovereignty, borders still delineate areas of legal competence. Borders encompass the territoriality necessary to the concept of the "state." They provide a key element in the structure of the global system—mapping the number and arrangement of the territorial units upon which all humans live. Thus, borders are central to a spatial approach to international politics, by setting out the location and arrangement of states, and their distances from one another. Borders both facilitate and constrain human interaction in conflict and trade, in war and in peace.