In the middle of the program window, the surface of the current page is visible in the work area, measured in pixels by a pair of rulers.
At the very bottom of the window, a status bar reflects your interaction with the program and offers a number of informative readouts.
The rest of the program window is made up of individual sub-windows known as panes. Each pane can be docked, tabbed, pinned, resized, dragged, and even made to float on top of the design environment.
Tip: To show/hide panes, use the View menu (View > Panes).