Since advice is central to what we are discussing here, it might be worthwhile to spend some time simply thinking about what advice is, what are the different types of advice we might come upon in our daily lives, and how advice is treated by different academic disciplines. That is what we do here. We ... first define what advice is, then categorize advice into some common-sense categories without expecting our categories to be either exhaustive or mutually exclusive. Finally, we discuss the way advice is treated in the economics and psychology literature, and contrast their approaches to the topic. In our next chapter, we turn our attention to conventions of behavior and the intergenerational games determining them.