Oil is a Fossil fuel which comes from the remains of the dead, mostly plants that lived billions of years ago. Rich Capitalists take a stab at the ground and let the oil squirt out, regardless of who lives above it. The oil gets burnt in order to make money which adds to Global warming and kills the environment. Capitalists and their supporters made up lies about Iraq, involving WMD so they had an excuse to invade the country and get oil.
Petrol, gas in the USA is a type of oil.
Oil is also something we use to fry food and we add oil to salads. Olive oil especially is supposed to be good for our hearts. We shouldn't eat too much of it.