Just when you thought that you were getting the hang of the Buttons window and the 3D Viewport window, there are several more windows to learn about. Have no fear; we will gently guide you through this book and teach you about these windows as the need arises. For now, you only need to know one of them to be aware of your many options.
In the 3D viewport window, you'll see a button on the header all the way to the left that has a grid on it (if not, click on a window separator with the RMB or MMB and choose "Add Header"). That button allows you to switch window types. Click on it with the LMB and you will see a number of different window types to which you can change. Try some of the different window types; you will learn about their relevance in time.
Change the window back to the 3-Dimensional Viewport before moving on to the next tutorial.