These lectures give an introduction to Gravitational Lensing. We discuss
lensing by point masses, lensing by galaxies, and lensing by clusters and
larger-scale structures in the Universe. The relevant theory is developed and
applications to astrophysical problems are discussed.Comment: revised version: references updated, some new results included; 53
pages without any figures; complete versions can be found at
http://www.mpa-garching.mpg.de/Lenses/Preprints/JeruLect.htm
