What is FIRE?

One of the questions raised inside my mind for years I could remembered. What actually is fire is? Why they burn, with warm colour, some time even with unique colors. Why we often relate fire with destructive? Of course, Hellfire have word “fire” in it. But what fire is? At least the fire we see in this world. It is definitely not a solid matter while not even a liquid, they might be gas but we can see fire through naked eyes, it also not a plasma/lightning which produced by electrostatic charges. After all, fire is the byproduct from chemical reaction between oxygen and carbon compounds producing heat, carbon dioxides and ash while emitting photons. Then, fire might be just a illusion which our eyes perceived that our brain pictures it so we could understand. But why? It must be a reason. Is it just the brain’s way giving us a warning or maybe there is something that we didn’t know yet.