From what I understand, a big part of the issue is that brokerages have allowed traders to short almost 150% of GameStop's actual shares in circulation.
So hedge funds are shorting the stock, but enough people are holding their shares that, as the stock price rises, it forces the traders to close out their short positions early or risk losing everything. Since closing out a short position means having to buy the stock back, those buys push the stock price even higher.
It gets really insane when you realize that it's impossible for everyone who has shorted the stock to buy it back because there are 50% more shorts out there than there are actual shares. So as short sellers panic and want out, it drives the price even higher.
If enough people with actual shares hold, there may not be any shares for short sellers to buy, or at least a very restricted supply, also driving the price up.
At this point it's a game of chicken. The longer all the holders hang on, the higher the price goes, the bigger the panic of short sellers. This is what's called a "short squeeze" because all the short sellers are getting squeezed by the stock price rising. Hedge funds are already trying to sow fear about GameStop by using the media to push rhetoric that the stick is poised for a big drop and also by trying to direct people's attention to other stocks favorable to a short squeeze in order to try and get some holders to think they've either reached the top and sell, or panic sell, or just sell because they're satisfied with the gains they have.
This is a historic event because on Friday, retail stock investors bankrupted a hedge fund company. That company had to secure an additional $3 Billion from other hedge funds to stay in business.
The general sentiment on WallStreetBets is to not blink, and hold the stock until it hits $1000 per share. Presumably at that point they would all sell, though the mechanics of that are unclear to me. Someone has to be buying, and at $1000 per share will there still be short sellers looking to close out their position and save a little face?
It's been fascinating as hell to watch, I'll say that. Depending on how it plays out, this situation may very well end up in business textbooks as the perfect example of the risk associated with shorting a stock en masse, as hedge funds have been. The rise in trading apps like Robinhood have made it easier than ever for the regular Joe to implement the kinds of strategies that hedge funds use to manipulate a stock price, all of it perfectly legal.