The term WHAT FUEL PROVIDES can be answered with the 6-letter word ENERGY. ENERGY is a form of power that can be used to do work, such as powering machines or providing heat. It is found in many forms, including chemical, mechanical, electrical, and thermal ENERGY. Fossil fuels, such as coal, oil, and natural gas, are the most common sources of ENERGY used today. Renewable ENERGY sources, such as solar, wind, and hydropower, are becoming increasingly popular as they are more sustainable and have less of an environmental impact.