1-Shorting a stock- Short sellers borrow shares & sell them immediately w/ the intent of purchasing back at a lower price. If the price doesn't go down, they can wait or cover it by buying those shares back (results in a loss)

2-The Squeeze- money flow determines the price of a stock. More money in = higher price. When a frenzy of buy orders come in all at once, it puts pressure on short positions, they must cover big interest payments (wait it out), or cover their position (buy)

3-Combined massive liquidity (easy to obtain $ via low borrowing rates) + cult-like buying driven by our MEME-centric culture + bloated hedge funds covering their massive short positions (buying) & you get irrational behavior in a stock like we've seen in $AMC & $GME