Fossil fuels are hydrocarbon-containing substances that are naturally formed in the crust of the planet from the remains of extinct plants and animals.
When organic material that has been buried deep in the soil is exposed to heat and pressure over millions of years, fossil fuels are created.
These fuels, which are located in the crust of the Earth, contain hydrogen and carbon that can be burned to produce energy.
Coal, oil, and natural gas are a few examples of fossil fuels.