  We present a pedagogical review of neutrino physics. In the first lecture we
describe the theoretical motivation for neutrino masses, and explain how
neutrino flavor oscillation experiments can probe neutrino masses. In the
second lecture we review the experimental data, and show that it is best
explained if neutrinos are massive. In the third lecture we explain what are
the theoretical implications of the data, in particular, what are the
challenges they impose on models of physics beyond the SM. We give examples of
theoretical models that cope with some of these challenges.
