Lindner and Aichholzer provide an introductory overview of the theoretical and conceptual foundations of electronic democracy, thereby providing analytical insights on the interplay between Internet-based communication and democratic processes. To this end, different normative views, aims and approaches of e-democracy are presented and systematically related to the central tenets of the main models of democracy. As e-participation plays an essential role in most conceptions of e-democracy, a typology of Internet-based citizen involvement is developed, thereby structuring the diversity of e-participation practices. Given the growing relevance of Web 2.0 and social media, the chapter discusses to which degree they are able to support core democratic functions of public communication-namely public critique, legitimation, and integration-by exploring the effects of social media usage on the quality of deliberation, political activism and political behaviour. In view of phenomena such as "personalised politics", echo chambers and deliberate misinformation, the authors call for effective political, educational and regulatory responses to the democratic challenges social media increasingly pose. 2.1 Organisation and Theoretical Framework This chapter provides an introductory overview of the basic concepts, which will be applied in the ensuing chapters of this volume. This includes a brief introduction of the key characteristics of liberal, participatory and deliberative democracy, with the aim of providing conceptual orientation regarding the different concepts of e-democracy that will be dealt with in greater detail in this book. A comprehensive account and discussion of the rich political and theoretical debates on democracy is