  Neutrinos are amongst the most abundant particles in the universe. The fact
that they are massive particles proves that the Standard Model is an incomplete
theory and needs to be extended. This thesis focuses on the study of neutrino
properties from the available data from laboratory experiments and cosmological
observations. It also presents sensitivity studies for future neutrino
experiments. The first part covers the status of the determination of the
oscillation parameters in the three-neutrino framework, the mass ordering and
the absolute mass scale. A second part is devoted to other neutrino properties
predicted in neutrino mass models. The topics covered include the study of
spin-flavour precession in solar neutrinos from non-zero neutrino magnetic
moments, the prospects for neutrino non-standard interactions with quarks from
the solar sector and the expected limits on CPT violation from a separate
analysis of neutrino and antineutrino data. Regarding cosmology, the impact of
non-standard interactions with electrons and a non-unitary three-neutrino
mixing matrix in the process of neutrino decoupling are addressed. Finally, a
third part explores possible connections between dark matter and neutrinos. The
existence of dark matter has been proven indirectly via its gravitational
effects. This thesis presents two studies that explore how neutrinos could
probe the fraction of dark matter that could exist in the form of primordial
black holes and the experimental signatures expected from a hypothetical
coupling between neutrinos and an ultralight scalar dark matter candidate.
