  Major advances have been made in the field of gamma-ray bursts in the last
two years. The successful discovery of X-ray, optical and radio afterglows,
which were predicted by theory, has made possible the identification of host
galaxies at cosmological distances. The energy release inferred in these
outbursts place them among the most energetic and violent events in the
Universe. Current models envisage this to be the outcome of a cataclysmic event
leading to a relativistically expanding fireball, in which particles are
accelerated at shocks and produce nonthermal radiation. The substantial
agreement between observations and the theoretical predictions of the standard
fireball shock model provide confirmation of the basic aspects of this
scenario. The continued observations show a diversity of behavior, providing
valuable constraints for more detailed, post-standard models which incorporate
more realistic physical features. Crucial questions being now addressed are the
beaming at different energies and its implications for the energetics, the time
structure of the afterglow, its dependence on the central engine or progenitor
system behavior, and the role of the environment on the evolution of the
afterglow.
