  The discovery by the BeppoSAX satellite of X-ray afterglow emission from the
gamma-ray burst which occurred on 28 February 1997 produced a revolution in our
knowledge of the gamma-ray burst phenomenon. Along with the discovery of X-ray
afterglows, the optical afterglows of gamma-ray bursts were discovered and the
distance issue was settled, at least for long $\gamma$-ray bursts. The 30 year
mystery of the gamma-ray burst phenomenon is now on the way to solution. Here I
rewiew the observational status of the X-ray afterglow emission, its mean
properties (detection rate, continuum spectra, line features, and light
curves), and the X-ray constraints on theoretical models of gamma-ray bursters
and their progenitors. I also discuss the early onset afterglow emission, the
remaining questions, and the role of future X-ray afterglow observations.
