  This review is focused on neutrino mixing and neutrino oscillations in the
light of the recent experimental developments. After discussing possible types
of neutrino mixing for Dirac and Majorana neutrinos and considering in detail
the phenomenology of neutrino oscillations in vacuum and matter, we review all
existing evidence and indications in favour of neutrino oscillations that have
been obtained in the atmospheric, solar and LSND experiments. We present the
results of the analyses of the neutrino oscillation data in the framework of
mixing of three and four massive neutrinos and investigate possibilities to
test the different neutrino mass and mixing schemes obtained in this way. We
also discuss briefly future neutrino oscillation experiments.
