Lecture Notes, Summer School on Effective Theories and Fundamental
Interactions, Erice, 1996. The application of effective field theory methods to
the low energy structure of QCD is discussed. I emphasize the universal
structure of the corresponding effective Lagrangian and then discuss the
physics of the effective coupling constants. The implications of the effective
theory for the masses of the light quarks are analyzed in some detail.Comment: 30 pages, 3 postscript figure
