  A summary of how black holes grow in full, non-linear general relativity is
presented. Specifically, a notion of "dynamical horizons" is introduced and
expressions of fluxes of energy and angular momentum carried by gravitational
waves across these horizons are obtained. Fluxes are local and the energy flux
is positive. Change in the horizon area is related to these fluxes. The flux
formulae also give rise to balance laws analogous to the ones obtained by Bondi
and Sachs at null infinity and provide generalizations of the first and second
laws of black hole mechanics.
