About 1827, the use of matches, a friction method, came into use. Fire can be started by using a lens to focus sunlight on combustible material. Many cultures use dried animal dung as a fuel. LPG means liquid propane gas. It is made up of carbon and hydrogen.
Propane is under pressure so that it becomes a liquid and is stored in a pressurized tank.
Methane is a major component of coal gas. Methane, like propane, consists of carbon and hydrogen. A molecule of methane has only one carbon atom while a propane molecule has three carbon atoms. You can probably guess that octane has eight carbon atoms per molecule. Some fire extinguishers contain bicarbonate of soda, treated to prevent caking.