I know, it's enough to put someone to sleep when you mention the stock market, never mind getting into the intricacies of it.
What happened, at a basic level, was that some guys on Reddit found out that a big hedge fund was shorting GameStop's stocks — in effect, betting against the company and in a position to make money should it fail.
So, the Reddit users banded together to drive up the price of GameStop, causing those hedge fund bigwigs to lose billions of dollars in a matter of days, while the Reddit crowd gained. As the news started to spread and regular folks started getting in on the action and making money, trading apps like Robinhood cut off access.