What is an ETF?
An ETF or Exchange-Traded Fund is a collection of assets like stocks, bonds, or commodities that are often designed to track an index, sector, or investment strategy. They are like mutual funds, but can be traded on an exchange just like stocks, and often have much lower fees compared to mutual funds. For example, the SPDR S&P 500 ETF tracks the S&P 500 index which is a market-capitalization-weighted index of the 500 largest publicly-traded companies in the U.S.
ETFs allow you to invest in a particular theme, sector, or geography. For example, EWJ is the iShares MSCI Japan ETF which enables you to take exposure in Japanese equities. Similarly, FINX is an ETF that invests in Fintech sector.
You can learn more about ETFs here.