Why did a WTI contract fall below zero in April 2020?

Demand collapsed and storage was full

Oil prices jump. Which country is most likely to benefit?

A big oil exporter like Saudi Arabia

Oil is in your bus fare, your phone case and the price of food trucked to your local shop. That's why its price moves whole economies.
Oil is priced in US dollars per barrel (about 159 litres). The two benchmarks: WTI (US) and Brent (North Sea), a reference for much of the world's oil.
Supply and demand rule. Production cuts by the OPEC+ group or wars push prices up; recessions and new supply push them down.
Real example: in July 2008 WTI hit about US$145. By December, as the financial crisis crushed demand, it was under US$35: a fall of over 75% in five months.
In April 2020, with the world in lockdown and storage tanks full, one WTI contract closed at about minus US$37. Sellers paid buyers to take oil away.
Common mistake
Mistake: thinking high oil prices are bad for everyone. Exporters like Saudi Arabia, Norway or Nigeria earn more; importers like India, Japan or Indonesia pay more.
Key takeaway
Oil is global supply and demand plus politics, priced in dollars. It can swing wildly, even below zero.

Oil is priced in... US dollars per barrelOil trades worldwide in dollars, per barrel of about 159 litres.
Why did a WTI contract fall below zero in April 2020? Demand collapsed and storage was fullHolders of contracts about to expire had nowhere to store oil, so they paid others to take it.
Production cuts usually push oil prices... UpLess supply for the same demand means buyers compete harder for each barrel.
Oil prices jump. Which country is most likely to benefit? A big oil exporter like Saudi ArabiaExporters earn more per barrel; importers have to pay more.