what is oil

Oil, also known as petroleum or crude oil, is a fossil fuel and a nonrenewable source of energy. It is primarily composed of hydrocarbons and is formed from the remains of ancient marine organisms, such as plants and animals, that lived millions of years ago in a marine environment. Over time, the remains of these organisms were covered by layers of sand, silt, and rock, and the heat and pressure from these layers turned them into crude oil or petroleum. This process took place before the existence of dinosaurs. Crude oil and other hydrocarbons exist in liquid or gaseous form in underground pools or reservoirs, as well as in tiny spaces within sedimentary rocks and near the earths surface in tar sands. Petroleum products are fuels made from crude oil and the hydrocarbons contained in natural gas. These products can also be made from coal, natural gas, and biomass. After crude oil is extracted from the ground, it is sent to a refinery where different parts of the crude oil are separated into usable petroleum products. These products include gasoline, jet fuel, heating oil, and various other items used in everyday life, such as plastics and paints. Oil is a major component of modern civilization and is used for transportation, heating, and the manufacture of various materials.