• After decades of doubt, neutrino oscillations were confirmed through several experiments:
• In 1998, Superkamiokande experiment, a giant (50,000 ton) water detector confirmed that neutrinos created in the atmosphere undergo neutrino oscillations.
• In 2001, SNO experiment, a very large detector in Canada, detected all three neutrino types (electron, muon and tau neutrinos) from the sun and their numbers added up to the correct number expected from the power production in the sun.
• This was the final proof that neutrino oscillations are the correct solution for the solar neutrino puzzle. 
• The most important consequence of neutrino oscillations is that:

Neutrinos have mass!

• Oscillations of neutrinos are only possible if  the three neutrino flavors (types) have different masses.

If the neutrino masses were  the same (or zero), there would be no mechanism for the neutrino flavor wave state to oscillate out of phase and turn into a different type, and the initial neutrino would always be detected.