Phenomenology of neutrino oscillations

This review is focused on neutrino mixing and neutrino oscillations in the light of the recent experimental developments. After discussing possible ty pes 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 oscilla tions that have been obtained in the atmospheric, solar and LSND experiment s. We present the results of the analyses of the neutrino oscillation data in the framework of mixing of three and four massive neutrinos and investig ate possibilities to test the different neutrino mass and mixing schemes ob tained in this way. We also discuss briefly future neutrino oscillation exp eriments.