I'll try to put it in layman's terms:

-A company tried to "borrow" (not buy yet) stocks from Gamestop (GME). - The terms are that the company can sell the stock, but has to buy it back at an agreed upon date at the price it is in that date. - The way this works is if the stock is lower on the date of purchase than when the company sold it the company can pocket the difference.

SO

• they tried to do this to GME, but this time they both over-extended and allegedly blatantly announced they were doing it
• Wall Street Bets found out, and started buying a shit load of GME stock which increases demand which increases price in the short term.
• so now these companies HAVE to buy the stock back at a MASSIVE MARKUP from when they sold it resulting in big losses.