  These are expanded notes of lectures given at the summer school "Gif 2000" in
Paris. They constitute the first part of an "Introduction to supersymmetry and
supergravity" with the second part on supergravity by J.-P. Derendinger to
appear soon. The present introduction is elementary and pragmatic. I discuss:
spinors and the Poincar\'e group, the susy algebra and susy multiplets,
superfields and susy lagrangians, susy gauge theories, spontaneously broken
susy, the non-linear sigma model, N=2 susy gauge theories, and finally
Seiberg-Witten duality.
