Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How can I buy shares of oil? I'm told it's done through ETFs. How's that related to oil prices per barrel?
The papers you would need to buy are called 'futures', and they give you the right to buy (or sell) a certain amount of oil at a certain location (some large harbor typically), for a certain price, on a certain day. You can typically sell these futures anytime (if you find someone that buys them), and depending on the direction you bought, you will make or lose money according to oil rice changes - if you have the future to get oil for 50 $, and the market price is 60, this paper is obviously worth 10 $. Note that you will have to sell the future at some day before it runs out, or you get real oil in some harbor somewhere for it, which might not be very useful to you. As most traders don't want really any oil, that might happen automatically or by default, but you need to make sure of that. Note also that worst case you could lose a lot more money than you put in - if you buy a future to deliver oil for 50 $, and the oil price runs, you will have to procure the oil for new price, meaning pay the current price for it. There is no theoretical limit, so depending on what you trade, you could lose ten times or a thousand times what you invested. [I worded that without technical lingo so it is clear for beginners - this is the concept, not the full technical explanation]