Navigation pane in Word 2010 and Word 2013 is quite useful feature as users can do the following this
- Search document
- Browse the headings in document.
- Browse the pages in document.
- Browse the results from the current search.
But in case if your Word application does not show the navigation pane then you can unhide it using the View menu option. To turn on the navigation pane, from the home menu, navigate to View menu and then to Show section. Mark checkbox with label as Navigation Pane and this would display it on the sidebar.