  The impacts of the light sterile neutrino hypothesis in particle physics and
cosmology are reviewed. The observed short baseline neutrino anomalies
challenging the standard explanation of neutrino oscillations within the
framework of three active neutrinos are addressed. It is shown that they can be
interpreted as the experimental hints pointing towards the existence of sterile
neutrino at the eV scale. While the electron neutrino appearance and
disappearance data are in favor of such a sterile neutrino, the muon
disappearance data disfavor it, which gives rise to a strong
appearance-disappearacne tension. After a brief review on the cosmological
effects of light sterile neutrinos, proposed signatures of light sterile
neutrinos in the existing cosmological data are discussed. The keV-scale
sterile neutrinos as possible dark matter candidates are also discussed by
reviewing different mechanisms of how they can be produced in the early
Universe and how their properties can be constrained by several cosmological
observations. We give an overview of the possibility that keV-scale sterile
neutrino can be a good DM candidate and play a key role in achieving low scale
leptogenesis simultaneously by introducing a model where an extra light sterile
neutrino is added on top of type I seesaw model.
