Gauge invariance is a powerful tool to determine the dynamics of the
electroweak and strong forces. The particle content, structure and symmetries
of the Standard Model Lagrangian are discussed. Special emphasis is given to
the many phenomenological tests which have established this theoretical
framework as the Standard Theory of electroweak interactions.Comment: Updated version of the lectures given at the 2006 European School of
High Energy Physics (Aronsborg, Sweden, 18 June - 1 July 2006) and at the 4th
CERN - CLAF School of High Energy Physics (Vina del Mar, Chile, 18 February -
3 March 2007). 50 pages, 36 figure
