The Storyboard is where you can see all the pages in your presentation and manage them. The right hand panel contains Nav Bar section. In this section gives the ability to manage your Table of Contents (TOC).
TOC allows the ability to view all pages in a presentation to quickly navigate.
You now have the option to display the TOC in Presentation. Simply turn on "All Pages Button".
When "All Pages Button" is enabled, notice the TOC option will be displayed in Nav Bar.
You don't want to see TOC in your nav bar.. No Problem. Simply turn off "All Pages Button" option.
When "All Pages Button" is disabled, notice the TOC is no longer visible.