The following is meant to give an overview over our special volume. The first three sections 1-3 are intended to give a general overview over the physical motivations behind this direction of research, and some of the developments that initiated this project. These sections are written for a broad audience of readers with interest in quantum field theory, assuming only very basic knowledge of supersymmetric gauge theories and string theory. This will be followed in Section 4 by a brief overview over the different chapters collected in this volume, while Section 5 indicates some related developments that we were unfortunately not able to cover here.Due to the large number of relevant papers the author felt forced to adopt a very restrictive citation policy. With the exception of very few original papers only review papers will be cited in Sections 1 and 2. More references are given in later sections, but it still seems impossible to list all papers on the subjects mentioned there. The author apologises for any omission that results from this policy. A citation of the form [V:x] refers to article number x in this volume.