  The recent wide recognition of the existence of neutrino oscillations
concludes the pioneer stage of these studies and poses the problem of how to
communicate effectively the basic aspects of this branch of science. In fact,
the phenomenon of neutrino oscillations has peculiar features and requires to
master some specific idea and some amount of formalism. The main aim of these
introductory notes is exactly to cover these aspects, in order to allow the
interested students to appreciate the modern developments and possibly to begin
to do research in neutrino oscillations.
