The first step in delineating the boundaries of public diplomacy is to ground it firmly as a diplomatic practice. In this chapter, I suggest that, for the sake of analytical coherence, public diplomacy activities must satisfy the following conditions: communication must take place between groups separated by geopolitical boundaries; the political agenda must be for public or collective interests represented by institutionalized actors with intentionality, ultimately to influence or support foreign policies. I explain these conditions to distinguish public diplomacy from other forms of human interactions.