In the context of gas usage, what does "combustion" refer to?

Combustion refers specifically to a chemical reaction in which a substance, typically a fuel such as gas, reacts with oxygen to produce heat and light. This process is fundamental to various applications including heating, cooking, and powering engines. During combustion, the fuel undergoes a transformation, releasing energy in the form of heat, which can then be utilized for various practical purposes.

The other options focus on different aspects related to gas usage that do not encompass the actual reaction process. Gas extraction pertains to the methods of obtaining gas from natural deposits, while gas storage refers to how gas is contained for safety and convenience. Purification involves removing impurities from gas to make it safe for use, but none of these options capture the essence of combustion, which is the transformative reaction itself.