  The pure leptonic or semileptonic character of tau decays makes them a good
laboratory to test the structure of the weak currents and the universality of
their couplings to the gauge bosons. The hadronic $\tau$ decay modes constitute
an ideal tool for studying low--energy effects of the strong interactions in
very clean conditions. New physics phenomena, such as a non-zero $m_{\nu_\tau}$
or violations of conservation laws can also be searched for with tau decays.
The present experimental and theoretical status of tau physics is summarized.
