This book is divided into ten chapters. The objective is this book is to provide a brief outline of the concepts and the principles as well as the description of the established institutional framework. In particular, it presents the institutional structure of social security as well as its basic blueprint along with its recent developments. The taxonomy of pension arrangements is presented by giving emphasis on its legal status, format, type of arrangement, and type of coverage. In fact, the same book places the development of social security in a historical context. A particular emphasis is given to the history of European social security systems, which shaped social security systems worldwide. To complement the historical analysis, this book introduces the theoretical approaches and concepts that have emerged in the social security field. The traditional classification of welfare states is being addressed through a path-dependency perspective. Finally, the welfare states are described briefly under cultural, social, economic, and political prism, pinpointing their deficiencies and mapping their patterns.