We review the conformal field theory approach to entanglement entropy. We
show how to apply these methods to the calculation of the entanglement entropy
of a single interval, and the generalization to different situations such as
finite size, systems with boundaries, and the case of several disjoint
intervals. We discuss the behaviour away from the critical point and the
spectrum of the reduced density matrix. Quantum quenches, as paradigms of
non-equilibrium situations, are also considered.