Combustion -

Combustion is an exothermic, high-temperature chemical reaction involving fuel and an oxidant that produces light and heat. It is essential for modern energy production and occurs through various forms, such as rapid, spontaneous, explosive, or slow processes. Combustion

To summarize, for combustion to occur three things must be present: a fuel to be burned, a source of oxygen, and a source of heat. NASA (.gov) What is Combustion? | Ansys Combustion