  In these lectures we give a discussion of the structure of the electroweak
standard model and its quantum corrections for tests of the electroweak theory.
The predictions for the vector boson masses, neutrino scattering cross sections
and the $Z$ resonance observables are presented in some detail. We show
comparisons with the recent experimental data and their implications for the
present status of the Standard Model. Finally we address the question how
virtual New Physics can influence the predictions for the precision observables
and discuss the minimal supersymmetric standard model as a special example of
particular theoretical interest.
