Question

What is natural gas?

Answer 1

Natural gas is - as the word says - gas that occurs naturally.

When organic material decomposes in the absence of air, this gas is formed, mainly in the form of methane `CH_4`. Something like this happens in the intestines of herbivores. Methane usually gets into the atmosphere (cow farts) where it is a greenhouse gas, believed to be worse than `CO_2`.

If the organic material got trapped millions of years ago, and the gas cannot escape because there is a gas-tight layer above it, it stays underground, and tends to collect in the higher places under the gas-tight layer (so-called gas-domes, or more popularly: gas bubbles).

These can be mined.

After pumping up the gas, it still has to be cleaned from impurities, and then it can be used for heating.

BTW: something similar creates oil, and often (but not allways) they occur together in the same region.