SPY is the largest ETF and the first U.S.-listed ETF to hit the market. With about $171.6 billion in assets under management and 128.6 million shares exchanging hands on average each day, it trades more than any other security, has the most liquid options market of any ETF and tight bid-ask spreads. SPY tracks the S&P 500 but potential investor should be aware that the ETF is structured as a unit investment trust and not a regulated investment company like other funds. Consequently, the structure prevents SPY from reinvesting dividends, holding securities that are not included in the index, like futures, or engage in securities lending. Moreover, the ETF has a one-month lag between the ex-dividend date and the payment of its dividends.

IWB follows the Russell 1000 Index, which includes 1,000 large- and mid-cap U.S. equities. Asset category breakdown includes 44.9% mega-caps 32.9% large-caps and 19.9% mid-caps.

VV tracks the CRSP US Large Cap Index, which follows the largest 85% of the U.S. stock market. The index has also been almost perfectly correlated with the S&P 500 and the Russell 1000 indices.

Lastly, SCHX reflects the Dow Jones U.S. Large Cap Total Stock Market Index, which includes the largest U.S. companies that make up about 85% of the U.S. stock market. Long-term investors may also note that SCHX is among the cheapest U.S.-listed ETFs available, with a 0.03% expense ratio.

Max Chen contributed to this article.