Fossil fuels are nonrenewable sources of energy that formed from ancient organisms. They include coal, oil, and natural gas. Coal is mined and then burned to produce heat to generate electricity. Oil ...Fossil fuels are nonrenewable sources of energy that formed from ancient organisms. They include coal, oil, and natural gas. Coal is mined and then burned to produce heat to generate electricity. Oil and natural gas can be extracted through conventional wells or through unconventional methods, such as fracking. Fossil fuel use harms human health as well as the environment.