These lectures describe the most important theoretical methods in b-physics.
We discuss the formalism of effective weak Hamiltonians, heavy quark effective
theory, the heavy quark expansion for inclusive decays of b-hadrons and,
finally, the more recent ideas of QCD factorization for exclusive nonleptonic B
decays. While the main emphasis is put on introducing the basic theoretical
concepts, some key applications in phenomenology are also presented for
illustration.Comment: 50 pages, Lectures given at the 55th Scottish Universities Summer
School in Physics, 7-23 August 2001, St. Andrews, Scotlan
