Natural resources are materials from nature that are used to make things humans need. They fall into two categories: renewable resources, which can be replaced, like solar, wind, water, and biomass; and non-renewable resources, like fossil fuels, that cannot be replaced at the same rate they are used. Fossil fuels like coal, oil, and natural gas were formed from ancient living organisms but take a long time to form, so they are considered non-renewable. Natural resources are important because humans rely on them directly and indirectly for basic needs like food, housing, and transportation.