In these lecture I review the general structure of electric-magnetic d
uality rotations in every even space-time dimension. In four dimension
s, which is my main concern, I discuss the general issue of symplectic
covariance and how it relates to the typical geometric structures inv
olved by N=2 supersymmetry, namely Special Kahler geometry for the vec
tor multiplets and either HyperKahler or Quaternionic geometry for the
hypermultiplets. I discuss classical continuous dualities versus non-
perturbative discrete dualities. How the moduli space geometry of an a
uxiliary dynamical Riemann surface, (or Calabi-Yau threefold) relates
to exact space-time dualities is exemplified in detail for the Seiberg
Witten model of an SU(2) gauge theory.