Fossil fuels are fuels prduced by natural processes by anaerobic decomposition of buried dead organisms.
Coal, oil and natural gas constitute the three major states of fossil fuels.
All these have been formed from organic remains of prehistoric plants and animals, under high pressure, high temperature conditions.
All three forms are excellent energy sources, upon which modern day civillization is based. Coal is used as a domestic as well as industrial fuel in all three forms: anthracite, bituminous and lignite.
Fractionated liquid petroleum is used as automobile and industrial fuel, in all of its variations, viz. gasoline, kerosene, diesel, light oil, heavy oil, green oil etc.
Natural gas is mainly methane, and is a component of domestic and industrial gas supply lines, for use as an easily accessible fuel.