A summary of the physical processes occurring in gravitational collapse supernovae is presented. Special emphasis is placed on those areas of nuclear physics in which experimental results will play the biggest role. The character of neutrino emissions in a supernova event is also detailed. Studies of the afternath of a supernova explosion, the birth of a neutron star, are examined: this is the phase in which most of the neutrino emissions occur. Finally, an analysis of the observed neutrino events is presented. The general conclusion is that the standard supernova and neutron star cooling calculations are in remarkably good agreement with experiment. There seems to be no reason to assume the observed bunching in the data is real. The observed low energy neutrinos, and the signal duration of several seconds, attest to the diffusion, not streaming, of the neutrinos from the lepton-rich neutron star. The deduced total energy emitted is about 3 × 1053 ergs to within 50% or so, just what is expected for a 1.4 Msolar neutron star.