Combustion is a chemical reaction chemical that occurs between a fuel and an oxidizing agent that produces energy, usually in the form of heat and light.
Substances that burn easily or catch fire easily are called combustible substances. Paper, clothes, wood, LPG are all combustible substances. Without these substances, a fire cannot be started.
A non combustible substance is that which is not capable of igniting and burning. Examples of non - combustible materials include Portland cement concrete, gypsum concrete or magnesite.