Most of us are used to hearing on the news about "the market" and how it did today, without really giving much thought to just what "the market" is. Of course, that term usually refers to the U.S. stock market, and that's typically measured by the Dow Jones Industrial Average index or the S&P 500 (SNPINDEX: ^GSPC) index.Savvy investors should know more than that, though, so here's a deeper dive into the S&P 500, so that you can make more sense of it and perhaps even invest in it, as none other than Warren Buffett has suggested you do.Image source: Getty Images.Continue reading