Fire extinguishing refers to the extinguishing of a fire. The chemical powder extinguisher is nowadays used for pretty much any type of fire, however appropriate fire extinguishing assumes analysing the fire class first, and then selecting a (environmentally harmless) extinguishing agent. For powder extinguishers, this means using particulate matter (ie sand, soil, ...), and for foam extinguishers, this means using a ecological soap mixed with water. CO² and FM 200 extinguishers can be used as is (already ecological). Both however only work in confined spaces (indoors).
Note: never use water with class B fires, the water can spread the combustible fuel making the fire larger. Foam with water can also not be used with B fires, for the same reason. CO² finally can be used indoors, but make sure not to use it when inside the room (can asphyxiate the user).