In this series of lectures the basic ideas of the $1/m_Q$ expansion in QCD ($m_Q$ is the mass of a heavy quark) are outlined. Applications to exclusive and inclusive decays are given.
Comments: Lectures given at the 35. Internationale Universit\"atswochen f\"ur Kern- und Teilchenphysik, March 2--9, 1996, Schladming, Austria, 36 pages and 3 figures, LaTeX source file and 3 postscript files packaged with uufiles. The complete paper, including figures, is also available via anonymous ftp at ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/
