The SPY is an ETF. An exchange traded fund (ETF) is the broad name for a kind of security that aggregates or tracks multiple stocks within an index, industry, or another grouping. SPDRs are a type of specific ETF issued by State Street Global Advisors that tracks a specific index such as the S&P 500. While ETFs may trade like ordinary shares of stock, they represent a portfolio of stocks and not just one company.