The Fed's ability to raise and lower short-term interest rates is its primary control over the economy.

The lower spreads mean lower costs for investors, because Nasdaq investors generally do not trade directly with one another. Instead, they usually buy and sell from market-makers, brokerage firms that flip shares between buyers and sellers and keep the spread for themselves.

Bigger spreads mean bigger gaps between what buyers pay and sellers receive. For example, a spread of 10 cents a share means that the buyer pays $100 more for 1,000 shares than the seller receives.

Alex Berenson Quotes