Regarding the question posed in this chapter’s title, the common response is often, “Oh, it’s the issue of quantum superposition that isn’t clear. Even top-tier physicists find it unclear, so it’s understandable”. However, from my experience teaching beginners, I realize that the points where beginners feel unclear are not the same as the ones that top-tier physicists struggle with. They are much more elementary. In this chapter, I will identify these elementary points of confusion and set the goals of this book accordingly.