Final answer:
Fossil fuels are non-renewable energy sources formed over millions of years from the organic matter of prehistoric organisms. Examples include coal, oil, and natural gas, which developed under high pressure and temperature conditions.
Step-by-step explanation:
Fuels formed by natural processes such as the decomposition of prehistoric organisms are called fossil fuels. Examples of fossil fuels include coal, oil, and natural gas. These energy sources originated from the organic matter of plants, algae, and cyanobacteria that were buried, heated, and compressed under high pressure over millions of years. The dead organic matter was then transformed into different types of fossil fuels depending on the combination of organic material present, burial duration, and the temperature and pressure conditions during decomposition.
Fossil fuels are considered non-renewable because they form over millions of years and are being used at a rate far exceeding their formation. Once these fuels are depleted, they cannot be replenished within a human timescale, underscoring the urgent need for alternative energy sources.