The notion of diplomacy, its roots, and some historical data bring the practice back to ancient Greece, to Roman times, to Byzantium, and its evolution in the rest of Europe. Contemporary diplomacy is the main instrument for conducting a state’s foreign policy, covering legal and political issues in particular, now extending thematically to areas such as the economy, industry, trade, ecology, sports, culture, energy, etc., on an ongoing basis. Modern diplomacy comes in many forms, based on the sources of international law, as international treaties and international customs.