When you assign text to be a Heading, of level 1, 2 etc. (by doing ⌘1, ⌘2… or choose Tag/Heading in iOS), Author changes the appearance of the Heading to what is specified in your chosen Style and - this is where the magic happens - Author makes your Heading into outlines:
Click on the Heading and all the text below it instantly curls up inside the heading.
You now have an automatic outline which you can even drag to different locations to re-order your document.
You can also move your cursor/mouse to the left side of the screen where an automatically generated Table Of Contents will appear. Click on a heading and your text jumps to that location. Move your cursor back to the centre of the screen and the Table Of Contents disappears, leaving you with your minimalist, distraction free environment.