  $\gamma$-ray bursts (GRBs) have puzzled astronomers since their accidental
discovery in the sixties. The BATSE detector on COMPTON-GRO satellite has been
detecting GRBs for the last four years at a rate of one burst per day. Its
findings has revolutionized our ideas about the nature of these objects. In
this lecture I show that the simplest, most conventional and practically
inevitable, interpretation of the observations is that GRBs form during the
conversion of the kinetic energy of ultra-relativistic particles to radiation.
The inner ``engine" that accelerates these particles is well hidden from direct
observations and its origin might remain mysterious for a long time.
