Oil continues to reign supreme as the world’s principal energy source. Its physical characteristics are such that it is a uniquely precious resource and we will show how and where it is used. This chapter presents the fundamental difference between resources and reserves, and their geographical distribution. Specifically, the United Convention of the Law of the Sea, a key framework for international policy, will be presented and we will show the consequences of its application. The various actors of the oil sector will be presented for understanding the technological revolution occurring in the following oil production sector. The typology of oil production contracts will also be explained. Finally, as crude oil cannot be used in its basic form it is important to describe its refining and the challenges, to which this key sector is confronted worldwide. In this chapter, we will analyse only the conventional oil situation. Shale oil and shale gas are so important that a full chapter will be devoted later to this subject.