Exact results on N=2 supersymmetric gauge theories

This is the introduction to the collection of review articles "Exact results on N=2 supersymmetric gauge theories". The first three sections 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 by a brief overview over the different chapters collected in this volume, while the last section indicates some related developments that we were unfortunately not able to cover.