So, here is the deal, basically numerous groups of subreddit groups oas well as other communities decided to short sell GameStop stock. The short positions caused the stock to fall dramatically. When the stock price fell other groups noticed and realized that the stock is being sold short and perhaps undervalued. Massive buying took place and all the short sellers needed to get back in the market and also purchase shares to cover their positions.
The great thing about these hyper volatile stock movements is great if you are on the winning side. If you are on the losing side you get get wiped out.