Duality in N = 2 SUSY SU(2) Yang-Mills theory: A pedagogical introduction

I review in considerable detail and in a hopefully pedagogical way the work of Seiberg and Witten on N = 2 supersymmetric SU(2) gauge theory without extra matter. This presentation basically follows their original work, except in the last section where the low-energy effective action is obtained emphasizing more the relation between monodromies and differential equations rather than using elliptic curves.