Public diplomacy is one of the most important concepts and prominent aspects of international relations in our time. The communication revolution and the explosion of information, the end of the Cold War, and the increase in the role and influence of the general public in foreign and international politics increased the importance and promotion of public diplomacy in international relations. Development of the concept of soft power also stimulated the study and debate about public diplomacy in theory and practice. Some claimed that with the concept of soft power, the concept and function of public diplomacy has become obsolete. Others, on the contrary, argue that soft power has increased the value and importance of public diplomacy. The production and development of digital technologies has fueled these discussions and debates again. A group believes that the interactive and symmetrical nature of these technologies has made the idea and focal point of public diplomacy to advance and support national interests irrelevant. On the other hand, another group believes that digital technologies have facilitated and strengthened public diplomacy. In this article, the concept, objectives, elements, tools, as well as different approaches and perspectives to public diplomacy is explained; Then its difference with related and similar concepts is examined. Finally, it is argued as a conclusion that theoretical, practical and technological developments, especially digital technologies, in international relations have not only reduced the importance of public diplomacy, but also increased its strategic value.