Oxygen and fire

In our common parlance fire burns producing light and heat.

This is what Sun does - it produces light and heat. It took humanity quite a while to learn to know the special kind of burning taking place inside Sun and other stars that produces such tremendous heat and brilliant light. The main development in stellar astrophysics took place quite recently in the 20th century AD and the science required some truly brilliant minds to develop. Thanks to these efforts we know today that Sun burns hydrogen in nuclear reactions and that there are also other significant types of nuclear burning going on in the stars and deep sky.


Oxygen in the heart of earthly fire
The fires we meet in everyday life here upon Earth under the heavenly oxygen mask. Learning not only how to use fire but also how to make fire must have been one of the greatest scientific inventions of early humanity. No other living species upon Tellus know to light fire without having fire at hand in the first place. The invention making pop-corn eating possible took place already in the Palaeolithic or Old Stone Age. Archaeologists are looking for hard evidence of man made fires already in Acheulean habitations but finding it is not an easy job.

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.Slower oxidative processes like rusting or digestion are not included by this definition.

The flame is the visible portion of the fire. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity will be different.
wikipedia

Combustion

The fire tetrahedron wikimedia

The scientific term is combustion from Latin combustionem (nom. combustio), a burning.

The fire tetrahedron: fires start when

1. a flammable and/or a combustible material 
2. in combination with a sufficient quantity of an oxidizer such as oxygen gas or another oxygen-rich compound (though non-oxygen oxidizers exist that can replace oxygen) 
3. is exposed to a source of heat or ambient temperature above the flash point for the fuel/oxidizer mix
4. and is able to sustain a rate of rapid oxidation that produces a chain reaction. 

Fire cannot exist without all of these elements in place and in the right proportions.
wikipedia

Combustion, the chemistry of oxidation, is very complex even fire appears to be such a familiar thing to us humans.