ETFs offer convenient and, in many cases, economical exposure to a variety of asset classes and investment strategies. However, in some cases investors unaccustomed to ETFs have been negatively surprised by the trading missteps that are possible when transacting these products. In this report, we seek to help investors understand some of the key differences between ETFs and traditional mutual funds by reviewing their mechanics, highlighting sources of tracking error, outlining fee and tax considerations, clarifying market impact, offering a set of key decision points for choosing between an ETF and a mutual fund, and discussing best practices for trading ETFs.