I realized that I hadn't yet made a super explanatory post on ETFs, let's fix it right away. Exchange-traded funds, or ETFs, have become increasingly popular in recent years. As a way for investors to gain exposure to a variety of different assets, sectors, and markets. According to data from the Investment Company Institute, ETF assets under management reached $4.5 trillion in 2020. Up from $1.8 trillion in 2015. Several key ETFs advantages help to understand this growth in popularity.