So far, most of the topics we have addressed in the book have centered on index-linked ETFs. This is because all the ETFs that were first introduced in the market tracked an underlying index benchmark, and as a result, ETFs became strongly identified with index-based investing. However, over the last few years there has been a steady increase in the number of active ETFs that are now gathering assets. This chapter will explain the basic concept of active ETFs. It will also address the difference between active ETFs and index-based active investing, in the context of the emerging investing mindset that we discussed in Chapter 2.