Erice: INTERNATIONAL SCHOOL OF NUCLEAR PHYSICS, 47th COURSE

Neutrino mixing, arising from the misalignment between flavor and mass eigenstates, leads to oscillations that firmly establish nonzero neutrino masses and physics beyond the minimal Standard Model. This talk provides an overview of the three-flavor mixing framework, parameterized by three mixing angles, two mass-squared differences, and a CP-violating phase. I will summarize the current global constraints from solar, atmospheric, reactor, and accelerator neutrino data, and highlight key open questions, including the neutrino mass ordering, the size of leptonic CP violation, and the possible existence of new physics beyond the Standard Model that next-generation experiments aim to address.