A propellant is a substance used to propel an object, such as a rocket or a projectile. Propellants can be divided into four categories: explosives, fuels, STEAM, and oars. An EXPLOSIVE propellant is a chemical compound that produces a rapid release of energy when ignited. Examples of EXPLOSIVE propellants include gunpowder and cordite. A FUEL propellant is a combustible material that releases energy when burned. Examples of FUEL propellants include gasoline, kerosene, and diesel. STEAM propellants are gases that are heated to create pressure, which is then used to propel an object. OAR propellants are mechanical devices that use the force of water to move an object forward.