Petroleum is another form of crude oil. And like crude oil, it is a fossil fuel. Petroleum was formed from the remains of ancient marine organisms just as coal and natural gas. The organic remains were transformed into carbon-rich substances over millions of years of intense heat and pressure to produce that which we rely on as raw materials for fuel and a vast variety of other products.Petroleum can be found in vast underground reservoirs where ancient seas once were. Petroleum is used to make products that are important in our everyday lives, like gasoline. Processed petroleum is a part of thousands of different items which include tires, refrigerators, life jackets, and anesthetics.