  The theory and phenomenology of light sterile neutrinos at the eV mass scale
is reviewed. The reactor, Gallium and LSND anomalies are briefly described and
interpreted as indications of the existence of short-baseline oscillations
which require the existence of light sterile neutrinos. The global fits of
short-baseline oscillation data in 3+1 and 3+2 schemes are discussed, together
with the implications for beta-decay and neutrinoless double-beta decay. The
cosmological effects of light sterile neutrinos are briefly reviewed and the
implications of existing cosmological data are discussed. The review concludes
with a summary of future perspectives.
