Oil is variously referred to as Crude, Brent, Petroleum and so on. It is a naturally occurring, yellow-to-black liquid found in geological formations beneath the Earth's surface. It is commonly refined into various types of fuels, chemicals and plastics. Components of petroleum are separated using a technique called fractional distillation.

Oil consists of hydrocarbons of various molecular weights and other organic compounds. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure over millions of years.

Petroleum has mostly been recovered by oil drilling for over 150 years. Drilling is carried out after numerous geological and seismic studies. It is refined and separated into a large number of consumer products, from gasoline (petrol) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum is used in manufacturing a wide variety of materials, and the world consumes almost 100 million barrels each day. The location of Oil deposits is uneven, the main producers are Russia, the US and the Organization of the Petroleum Exporting Countries (OPEC), comprised of Algeria, Angola, Ecuador, Equatorial Guinea, Gabon, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, D.R. Congo, Saudi Arabia, United Arab Emirates and Venezuela. The largest importers of Oil are the Asian nations of India, China and Japan.

Concern over the depletion of the earth's finite reserves of oil, and the effect this would have on a society dependent on it, is a concept known as peak oil.

It is widely acknowledged that the use of fossil fuels, such as petroleum, has a negative impact on Earth's biosphere, damaging ecosystems through events such as oil spills and releasing a range of pollutant emissions into the air during combustion.

The preeminent energy organizations including EIA, IEA, WEC and major oil companies conclude that Oil, along with other fossil fuels, will continue to provide the majority of world primary energy requirements until between 2040 - 2060.