  Gamma-ray bursts are associated with catastrophic cosmic events. They appear
when a new black hole, created after the explosion of a massive star or the
merger of two compact stars, quickly accretes the matter around it and ejects a
transient relativistic jet in our direction. This review discusses the various
types of gamma-ray bursts, their progenitors, their beaming and their rate in
the local universe. We emphasize the broad astrophysical interest of GRB
studies, and the crucial role of high-energy satellites as exclusive suppliers
of GRB alerts and initial locations.
