I’m no investor nerd but I know enough to sum things up like this: Short Sellers basically are betting that a company will do bad. Regular investors are betting that a company will do good. Various “retail” investors, meaning I believe non-professionals “davids”, found out that various hedge fund/institutional investors, aka Goliaths, were selling short in large dollar amounts. Through communication using reddit and other social media investors bought huge amounts of Gamestop stock causing it’s price to skyrocket (i.e. to “win/do good”). That caused the bad guys betting on Gamestop’s demise to lose a fortune.
It gets more complicated because there are controls that kicked in to limit their losses. Which means the goliaths had a regulatory mechanism to save themselves, whereas average investors like you and me don’t have that. And to make things even more fun, the retail investors used a very popular trading platform called Robinhood. Get it? 