The element that is combustible and commonly used in fireworks is potassium nitrate (KNO3). Potassium nitrate is an oxidizer, providing the necessary oxygen for combustion, which facilitates the rapid burning of other flammable materials present in fireworks. It is a key ingredient in various pyrotechnic formulations, allowing for the production of vibrant colors and effects when combined with different metal salts and fuels. The controlled reactions of potassium nitrate, along with other components, produce the loud sounds and spectacular visual displays that characterize fireworks. Its use dates back to ancient times, allowing for various cultural celebrations and events worldwide.