The Origin of Cosmic Fireworks

Gamma-Ray Bursts are the most remarkable explosions observed in our Universe. For a few seconds the burst's luminosity is comparable to the luminosity of the rest of the Universe combined. In this talk I describe the basic properties of Gamma-Ray Bursts focusing on their progenitors. Two well known groups of progenitors are Collapsars that are produce long bursts when a jet penetrate a collapsing massive star and neutron star mergers that produce short bursts. In addition there is a third group of low luminosity GRBs that are also associated also with a collapsing stars but in which case the burst are not produced via the well known Collapsar mechanism. We review the different mechanisms and the different bursts that they produce. I also discuss radio flares that arise from neutron star mergers in addition to gamma-ray bursts and their implications for the detection of gravitational waves from these sources.