Renewable fuels refer to energy sources that can be replenished naturally in a relatively short period, as opposed to non-renewable fossil fuels which are finite and take millions of years to form. Renewable fuels include biofuels such as ethanol and biodiesel made from plant materials like corn or soybeans, hydroelectric power generated by moving water, wind energy captured through turbines, geothermal heat pumps that use the earth's natural heat to provide heating and cooling, and solar energy harnessed through photovoltaic panels. These renewable sources of energy are considered more sustainable and environmentally friendly alternatives to traditional fossil fuels as they produce fewer greenhouse gas emissions and reduce our dependence on non-renewable resources.