Media are explored as a model to envision, to design, to formalize and to implement platforms for communities. We consider communities of both natural and artificial agents and aim at designing media which facilitate collaboration within such a community. Our approach is based on the media concept and the media model. The media concept envisions media as platforms for multi-agent systems and the media reference model determines the main components of a medium and guides its application as, e.g. for e-commerce or knowledge management. We present a formalization of those models that facilitates artificial agents to act according to the description given in this formalization. We explore the notion of community and various interrelation communities and their media. We discuss the representation of a community on a platform and how technology enables and influences the constitution of communities. We reconstruct communities on media and explore formalization, redesign and reconsideration of aspects of communities.