Heading levels can be used by screen readers like a table of contents for your page, allowing users to scan and skip content more easily.
At NYU Libraries, we have set our LibGuides system to have the following default headings (but your organization may not have this so you will see these heading levels in the Rich Text / HTML box):
There should only be one Heading 1 on the entire page (thus it make sense at NYU to have this set as the Page's heading).
So the first heading in any Rich Text HTML box (at NYU) will be a:
Is the first available heading level in the rich text editor.
You can also include an unstructured list:
Or you can include a numbered (structured) list:
This will add a sub-section under heading 3.