Outline View

Displays just the headings and subheadings in a document, providing organisation structure.
Useful when you are reorganising the content or moving sections etc.
Link (Outlining > Outline View)
Outlines can help you structure your document using "Heading" styles.
(View > Outline)

The Outline toolbar

A condensed form of the Outline toolbar will be displayed when you are not in Outline View.

The full Outline Toolbar will appear automatically when you are in Outline View.

For more details please refer to the dedicated Outlines section.