  In this contribution, I present a short overview of the theory of direct
nuclear reactions, with special emphasis on the case of reactions induced by
weakly-bound nuclei. After introducing some general results of quantum
scattering theory, I present specific applications to elastic, inelastic,
transfer and breakup reactions. For each of them, I first introduce the most
standard framework, followed by some alternative models or extensions suitable
for the case of weakly bound nuclei. A short discussion on semiclassical theory
of Coulomb excitation and its application to breakup of halo nuclei is also
provided.
