Big Hedge funds shorted Gamestop’s (GME) stock. That means they sold stocks before they had them, assuming the price they will buy them at would be lower than what they sold them for. People on reddit found out, started a mini-movement to buy GME stocks to jack price up. Big hedge funds are going to lose loads of money by Friday, especially since they sold more shorts than are available stocks to buy. They have to pay interest on shares they didn’t deliver.