  We give in this Chapter an overview of the problem of neutron star mass
distribution, the issue of the maximum mass as inferred from the existing
sample and the new gravitational wave events, and the connection with the
formation events. It is shown that at least two different mass-scales (and
possibly three) are favored by Bayesian and frequentist analysis, and the
resulting maximum mass on empirical grounds only is $\sim 2.5 M_{\odot}$,
making room for an interpretation of the lighter component of the GW190408
merger as a neutron star (as suggested by the GW event population analysis). We
discuss in some length the challenges for a theoretical construction of a stiff
equation of state and the status of available supernova explosions (single and
binary simulations) and AIC expected to provide the masses at birth.
