This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book provides basic information about the region - the territorial setting, the tribal population and its distribution. It includes a detailed discussion of the ecological and economic setting in the pre-dam period. The chapter examines the common pattern of exchange between lineage members in two spheres of economic activity: those concerning labour and consumption goods. It discusses and analyses the pattern of social differentiation that provided two categories of people, the ummar and religious shaikhs, with special sources of power over other categories. The chapter provides an account of the salient effects of the dam upon the ecological and economic setting and describes the basic features of the post-dam economy's agrarian development. It outlines of the new trends at the higher levels of administrative and tribal politics.