From Investopedia
"Quants" is Wall Street's name for market researchers who use quantitative analysis to develop profitable trading strategies. In short, a quant combs through price ratios and mathematical relationships between companies or trading vehicles in order to divine profitable trading opportunities.
During the 1980s, a group of quants working for Morgan Stanley struck gold with a strategy called the pairs trade. Institutional investors and proprietary trading desks at major investment banks have been using the technique ever since, and many have made a tidy profit with the strategy. It is rarely in the best interest of investment bankers and mutual fund managers to share profitable trading strategies with the public, so the pairs trade remained a secret of the pros (and a few deft individuals) until the advent of the Internet.
Online trading opened the lid on real-time financial information and gave the novice access to all types of investment strategies. It didn't take long for the pairs trade to attract individual investors and small-time traders looking to hedgetheir risk exposure to the movements of the broader market.
Pairs trading has the potential to achieve profits through simple and relatively low-risk positions. The pairs trade is market-neutral, meaning the direction of the overall market does not affect its win or loss. The goal is to match two trading vehicles that are highly correlated, trading one long and the other short when the pair's price ratio diverges "x" number of standard deviations - "x" is optimized using historical data. If the pair reverts to its mean trend, a profit is made on one or both of the positions.
