The compelling experimental evidences for oscillations of neutrinos  imply the existence of 3-neutrino mixing in  the charged current weak interaction Lagrangian. The phenomenology of 3-neutrino mixing, of the Dirac and Majorana CP violation in the lepton sector,  as well as the current data on the 3-neutrino mixing parameters, will be briefly reviewed. The theory of neutrino oscillations in vacuum and in matter will be briefly discussed. The open questions and the main goals of future research in the field of neutrino mixing and oscillations will be outlined. The prospects of searches for CP violation in neutrino oscillations and the problems of determination of the type of neutrino mass spectrum and of the nature - Dirac or Majorana, of massive neutrinos will be considered.