Theory of the Neutrino Mass

Theoretical aspects of neutrino physics are reviewed, with emphasis on possible explanations of the smallness of neutrino masses and of the peculiar mixing pattern observed in the lepton sector. Some theoretically motivated frameworks, such as those based on spontaneously broken discrete flavour symmetries, are discussed, stressing the importance of low-energy observables, like anomalous magnetic moments, electric dipole moments and lepton flavour violating transitions, to test further features of these models.