This chapter lays the groundwork for the chapters to come. In it is described the basics of how a visualization is constructed, giving a rough overview of the data pipeline and describing the components of a general visualization. I define a visualization in terms of a set of orthogonal features that can be composed to form a complete visualization. These “building blocks” include the coordinates system; the type of element (line, point, bar); color, shape, and other mappings from data to appearance; statistics; and paneling. These definitions allow us to talk about visualizations sensibly and precisely, as well as to classify visualizations by their features. In later chapters we will see how different choices of features serve different graphical goals, and we will then be able to compose the features we want to serve our goals, resulting in an effective visualization.