In 1605, Guy Fawkes and a group of co-conspirators attempted to blow up King James 1 and the Houses of Parliament in what has become known as the Gunpowder Plot. Before they were able to carry out their plan they were caught, and subsequently tortured and executed.
Every year since then on November the 5th, we have traditionally celebrated his notorious treasonous Gunpowder Plot failure by letting off fireworks and burning an effigy of 'Guy' on a bonfire. I pasted the above from www.guy-fawkes.com, that might give you bit more info. Regards MB