  Three schemes of neutrino mixings (oscillations) are proposed. The problems
of origin of angle mixings, with the law of energy-momentum conservation and
disintegration of neutrino as wave pocket are solved. These two schemes belong
to mass mixings schemes, where mixing angles and oscillation lengths are
expressed via elements of mass matrix. The third scheme belongs to the charge
mixings scheme, where mixing parameters are expressed via neutrino weak
charges, as it takes place in the vector dominance model. Using experiments we
must decide which of these schemes is realized indeed. Analysis of the
resonance enhancement mechanism of neutrino oscillations in matter is
performed. It is shown that there are no indications on existence of this
effect. It is shown that the supposition that the neutrinos are Majorana
particles is not confirmed by accelerator experiments. Then only mixings
(oscillations) between Dirac neutrinos with different flavors without sterile
neutrinos can be realized. Using all the present experimental data and the
theoretical results the problem of Sun neutrinos deficit is analyzed. The
conclusion is: the primary Sun $\nu_e$ neutrinos are converted into mixtures of
three types of neutrinos $\nu_e, \nu_\mu, \nu_\tau$ in approximately equal
quantities.
