Petroleum is oil — a fossil fuel that powers many vehicles and other machinery.
Petroleum is a fancy, technical word for something you've probably heard of: oil, an energy source. Petroleum is also known as crude, crude oil, fossil oil, and rock oil. A lot of petroleum is found in the Middle East, and people are always looking for new sources of petroleum. You have to drill for petroleum, because it's deep inside the Earth. There’s a limited amount of petroleum, so many people worry that we're going to use it all up.