Gamma-Ray Bursts are intense flashes of high-energy radiation, up to a sextillion times brighter than our sun at the peak of their emission. They are produced by massive fastly spinning stars at the end of their main sequence evolution, when the dying stellar core collapses into a newly born black hole. Some bursts are also thought to produce powerful neutrino bursts and distinctive chirps in gravitational waves. In this talk I will introduce the physics and observations of Gamma-Ray Bursts, discuss their role as multi-messenger objects, and describe the accomplishments and recent advances in computer simulations of such extreme events.