  I briefly review some recent progress in the theory of nonleptonic B decays.
After introducing the operator product expansion and the relevant effective
Hamiltonian, I discuss the domain of validity and the theoretical justification
of the factorization approximation and of its generalizations. Furthermore, I
review some general parameterizations of B decay amplitudes: the "diagrammatic"
approach and the formalism based on Wick contractions in the matrix elements of
four-fermion operators.
