When plants, dinosaurs, and other ancient creatures died, they decomposed and were buried, layer upon layer under the ground. Their decomposed remains gradually changed over the years. Fossil fuels are usually found below ground. Coal is either mined or dug out while oil and natural gas are pumped out. Coal is widely distributed and is easier to locate than oil and gas.
Fossil fuels take millions of years to make but burn and disappear in seconds.
Once they are used, they cannot be reused. People have irretrievably damaged the planet by extracting and burning these fuels. It is best not to waste fossil fuels as they are not renewable. We have to learn to conserve these sources of energy. Every year, millions of tonnes of coal is consumed as energy.