Neutrino masses mixing and oscillation

Neutrino mixing and basics of neutrino oscillations in vacuum are considered. Recent evidence in favour of neutrino oscillations, obtained in the solar and atmospheric neutrino experiments, are discussed. Neutrino oscillations in the solar and atmospheric ranges of δm2 are considered in the framework of the minimal scheme with the mixing of three massive neutrinos. The experiments on the measurement of neutrino mass via investigation of the high-energy part of the β-spectrum of tritium and experiments on the search for neutrinoless double β-decay are also discussed