There are four classes of fire extinguishers, and each category can put out a different type of fire.
Class A extinguishers will put out fires in ordinary combustibles such as wood and paper etc.
Class B extinguishers are for use on flammable liquids like grease, gasoline, and oil, so they best fit in gas stations.
Class C extinguishers are suitable for use only on electrically energized fires.
Class D extinguishers are for use on flammable metals.