What is an ETF? This is a question that most people ask when confronted with this specific topic. ETF funds (Exchange Traded Funds) have long been considered an alternative to traditional investment options for institutional investors. Rupert Thiery explains what an ETF is, how the market has developed in recent years, and provides an overview of how this type of fund can be categorized. In this way, Thiery enables the reader to navigate the rapidly growing market of ETF funds. The decision criteria for investing in ETF funds presented by Thiery serve as a guide for potential personal investments.