What it is: Stocks are ownership stakes in companies, and the overall stock market is measured by a number of indexes. The S&P 500, comprising 500 companies, is considered one of the broadest indexes and a prime indicator of how the stock market is faring.
Why it's important: Most retirement funds, like 401(k) plans and IRAs, grow and shrink based on the movement of stock prices. Stocks are also considered to be forward-looking indicators about the health of the overall market and economy.
Where we're headed: After rallying at a torrid pace from early 2009 into Spring 2010, stocks pulled back during the summer due to uncertainty about the health of the global economy. Stocks were back on a tear in the fall, as investors bet the Federal Reserve's latest plan to stimulate the economy will drive asset prices higher.
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Last updated November 23 2010: 10:39 AM ET