Memes

It's called shorting. At a high level you're basically betting on the stock going down (which is the opposite of buying a stock where you want it to go up). Normally you can only lose the amount of money you put in with stocks, but for shorting you may lose an "unlimited" amount of money depending on how high the price goes up (it's dependent on how much the stock goes up, but no stock goes up forever).

Shorting is a big part of the GME spike. Large trading firms were shorting the shit out of gamestop and so when WSB bought stocks en masse it lead to almost bankruptcy for some companies.

Not financial advice for obvious reasons

Seriously? It's just the knowledge you are lacking? If You have the funds to do it just meet with an investment banker and they can help you do it. Short selling is not something I would recommend doing yourself even "knowing enough about stocks". If you are serious about a short, you understand it's a pretty high level of risk but if there is a payout, the cost of bringing in a pro is well worth it.