When you sell a stock short you are betting its price will fall. Instead of buying a stock and waiting for it to climb, you reverse this process by borrowing shares, selling them, and buying them back to exit the trade.

In the search for trade ideas, it is often a good idea to look beyond a market’s basic price data. Sentiment, insider trading activity (the legal kind), and large-trader positions are just a few of the non-price factors traders use to gain additional insight on market action.

In the stock market, one such tool is short interest, which represents the number of open short positions in a stock or index — that is, shares that have been sold short but haven’t yet been bought back (“covered”).