What is an index? An index, like the DOW, the S&P500 or the NASDAQ, is a sample of stocks that provide insight into the broader market. When someone says "the market is up 10 points today", they are referring to an index. By measuring the compilation of similar stocks instead of just one or two stocks, a stock index provides information about that particular market or segment. One of the most talked about and popular indexes is The Dow Jones Industrial Average (DJIA) which consists of 30 of the biggest companies in the U.S. Stock indices are typically related by some commonality: for example, the Dow Jones Wilshire 5000 is an index that measures or tracks almost every publicly traded stock in the United States. The Morgan Stanley Biotech Index is a small index that follows the biotechnology market. Each stock index has a specific focus that can provide highly specific or very generalized information