  These lectures describe the use of effective field theories to extrapolate
results from the parameter region where numerical simulations of lattice QCD
are possible to the physical parameters (physical quark masses, infinite
volume, vanishing lattice spacing, etc.). After a brief introduction and
overview, I discuss three topics: 1) Chiral perturbation theory in the
continuum; 2) The inclusion of discretization effects into chiral perturbation
theory, focusing on the application to Wilson and twisted-mass lattice
fermions; 3) Extending chiral perturbation theory to describe partially
quenched QCD.
