Types of ETFs
ETFs that mirror indices like the stock or bond market have attracted by far the most investment from individual investors. A particularly popular way for investors to own a small stake of the American economy is to invest in ETFs that seek to mirror the S&P 500, an index of the 500 publicly-traded American companies with the highest market capitalizations. Since the S&P 500 naturally favors the largest companies, those who seek to diversify their equity with smaller companies may consider ETFs that track, say, the S&P 400, or the Russell 2000, which track, respectively, midcap and smaller publicly traded companies.