The natural resources primarily used for fuel are "fossil fuels," which include coal, oil, and natural gas. These resources are derived from the remains of ancient plants and animals, subjected to high pressure and temperature over millions of years. Fossil fuels are burned to produce energy for electricity, transportation, and industrial processes due to their high energy content. However, they contribute significantly to greenhouse gas emissions, raising concerns about climate change and environmental degradation. As a result, there is a growing emphasis on transitioning to renewable energy sources such as solar, wind, and hydroelectric power for a more sustainable future.