In chapter 2, we learned all about some basic design principles and concepts we’ll be using throughout this book, but this chapter is all about the data. To ensure everyone has the same basic understanding of data fundamentals, we’ll first touch on where you might find data out in the wild. Next, we’ll answer the question “What is data?” and talk about several basic data types. After that, we’ll learn how to describe the values of data and whether they are discrete or continuous and sequential or categorical. Finally, we’ll cover the two main types of data structures you’ll encounter in your visualization journey: tables and nested data.