Vacancies and self-interstitials in silicon have been studied extensively both experimentally and theoretically and many of their properties have been established. We review briefly some of the recent results obtained by ab initio calculations and by atomistic simulations using empirical interatomic potentials. These results yield a comprehensive picture of defect structure, migration paths, and relative contributions to self-diffusion. We elucidate the details of the atomic migration process by analyzing one of the migration paths of the self-interstitial in terms of the lattice normal modes (phonons). Finally, we report new calculations to clarify further similarities between crystals containing large concentrations of point defects and amorphous silicon. In addition to a notable trend in the density of crystals containing increasingly higher self-interstitial concentrations, we find strong similarities in the vibrational and structural properties.