[en] After summarizing the historical background of the neutrino concept and listing the main properties of the various kinds of particles and antiparticles of the neutrino group, the article deals mainly with the electron neutrinos which are produced in the solar interior as a by-product of the thermonuclear reactions of hydrogen. An outline of the p-p chain and CNO cycle reactions inside the sun is given, with the emphasis on the role of various branches of these processes in producing sufficiently energetic neutrinos which could be detected by Davis's method. Methods of neutrino detection based on two kinds of processes resulting from the weak interaction with matter - on inverse beta decay or on elastic scattering by electrons are considered and various experimental proposals concerning different substances suitable for neutrino detection are reviewed. Details of the Davis experiment are given and discussed. The possibilities of observational uncertainties in the neutrino counting rate are considered and various mechanisms which could explain the solar neutrino discrepancy are outlined. The influence of various physical factors upon the solar neutrino flux is discussed, starting with nuclear parameters and abundances of chemical elements in the Sun, up to the most speculative mechanisms involving apparently unrelated areas of physics. (U.K.)