This section is a brief review of the basics of two-dimensional diagrams of the sort used in introductory economics. Most economists call these diagrams "graphs," as do we. Almost every page of this online text contains a graph, so be sure you understand this section before you go on.

Why do we use so many graphs in introductory economics? Simply because they are a great way to make complicated points very easy to understand. If you take the time to fully understand the graphs used throughout this text, and learn to draw them for yourself, you'll be able to figure out the answer to almost any microeconomics question at the introductory level.

One of the reasons we were inspired to write this online text was that we wanted to make graphs available to students that are clear, easy to access, colorful, and animated. It's too expensive to put hundreds of good color graphs in printed texts and of course no way to make them animated. Much of the confusion our students experienced turned out to be the result of graphs drawn during class being incorrectly copied into lecture notes. With a wealth of correct graphs available online, problems due to incorrect graphs in notes become a thing of the past. Students find it easier to understand more complicated graphs when they are animated because they can see them being drawn, just as they would be in class, but they can view the process as many times as they wish online. Animation enables students to focus on the individual portions of the graph as they are completed, rather than having to comprehend the entire graph at once. Thus, the meaning of the entire graph becomes clear, and they are able to construct their own graphs for any situation.^{1} Students who learn with animated graphs find that they can understand complex static diagrams better as well.

^{1} One, in a long line of Economists' mottos: Never go to lunch with an economist, she'll spend the whole time drawing graphs on paper napkins.