In a chemical reaction, molecules (themselves composed of a set of atoms) are rearranged in new molecules by creating and/or removing bound between atoms. Creating/removing these bounds will either release or absorb some amount of energy. When the reaction release energy, it is an exothermic reaction. When it absorb energy it is an endothermic reaction. Fire is the energy released by some exothermic reactions, in the form of heat and light.
In a chemical reaction, molecules (themselves composed of a set of atoms) are rearranged in new molecules by creating and/or removing bound between atoms. Creating/removing these bounds will either release or absorb some amount of energy. When the reaction release energy, it is an exothermic reaction. When it absorb energy it is an endothermic reaction. Fire is the energy released by some exothermic reactions, in the form of heat and light.