  We review neutrino oscillation physics, including the determination of mass
splittings and mixings from current solar, atmospheric, reactor and accelerator
neutrino data. A brief discussion is given of cosmological and astrophysical
implications. Non-oscillation phenomena such as neutrinoless double beta decay
would, if discovered, probe the absolute scale of neutrino mass and also reveal
their Majorana nature. Non-oscillation descriptions in terms of spin-flavor
precession (SFP) and non-standard neutrino interactions (NSI) currently provide
an excellent fit of the solar data. However they are at odds with the first
results from the KamLAND experiment which imply that, despite their theoretical
interest, non-standard mechanisms can only play a sub-leading role in the solar
neutrino anomaly. Accepting the LMA-MSW solution, one can use the current solar
neutrino data to place important restrictions on non-standard neutrino
properties, such as neutrino magnetic moments. Both solar and atmospheric
neutrino data can also be used to place constraints on neutrino instability as
well as the more exotic possibility of $CPT$ and Lorentz Violation.
Weillustrate the potential of future data from experiments such as KamLAND,
Borexino and the upcoming neutrino factories in constraining non-standard
neutrino properties.
