You see it reported every day in the financial news: The Dow Jones Industrial Average (DJIA). And the Dow made headlines back on October 17, 2017, when it cracked the 23,000-point mark for the first time in its history. But what exactly is the DJIA and what do the fluctuations in points really mean?

The DJIA is a long-time barometer for the way the stock market is moving although it's not the only one, and it may not be the best measure of the thousands of stocks listed on the major exchanges. Some experts consider the Standard & Poor's (S&P) 500 and the NASDAQ to be more reliable indicators. Nevertheless, even if you don't put much store into whether the DJIA goes up or down on a given day, it does have an interesting history.

The Dow measures the movements of just 30 stocks. Traditionally, those have included the "blue-chip" companies considered to be the bedrock of the American economy. So, when the DJIA finally punched through the 23,000-point mark, it may have seemed like a triumph for the economy as a whole.