This is a market of stocks, and not just a "stock market".
All of these Indexes, from the Dow Jones Industrial Average to the Russell2000 Small-caps, are made up of components. There are 30 stocks in the Dow and 2000 stocks in the Russell2K, for example.
Are more of them going up? Are more of them making new highs? Are more of them showing bullish momentum characteristics? Are fewer and fewer components doing these things as the indexes make new highs? What about in downtrends? Are more stocks confirming the new lows in the indexes or are fewer and fewer stocks making new lows and showing bearish momentum characteristics as the market makes new lows?
The answers to these types of questions is what we call, "Market Breadth Analysis". There are a lot of ways to do this on all sorts of different time horizons. In this lesson we go over all the methods we use to decipher market breadth, which can be used by both individual traders and the largest financial institutions in the world.
This explanation is taken directly from Lesson 4 from the NEW Allstarcharts Charting School: