The substance used to create fireworks is gunpowder, also known as black powder. Gunpowder is a mixture of saltpeter (potassium nitrate), charcoal, and sulfur, which combusts rapidly, producing a large volume of gas and heat when ignited. In fireworks, this rapid combustion creates explosions, which can launch the firework into the sky. Additionally, various metal salts are employed to produce different colors during the display. Fireworks produce a combination of visual and auditory effects, making them popular for celebrations and festivities around the world.