A molotov cocktail (also called a petrol bomb]] is a simple firebomb made by pouring flammable liquid (usually gasoline) into a glass bottle and stuffing an old rag in the top, then lighting the rag and throwing it at a target. It then explodes in a large ball of fire.
Because of it's simplicity and the availability of the materials necessary, as well as being virtually impossible to detect or neutralize, it is very popular among rioters and insurgents.