WHAT'S A SHORT? It's how investors can make money off a stock falling. In a short sale, they borrow a share of GameStop and then sell it. Later, if the stock price does as they expect, they can buy the stock at a lower price and keep the difference. GameStop is one of the most heavily shorted stocks on Wall Street. WHAT'S A SHORT SQUEEZE? It's what happened with GameStop's stock. When a stock is very heavily shorted, a rise in its price can force short sellers to get out of their bets. To do that, they have to buy the stock, which pushes the stock even higher and can create a feedback loop. As GameStop's short sellers have gotten squeezed this month, smaller and first-time investors have been egging each other on to to keep the momentum going.