Headings and subheadings should provide an outline of page content, so users can understand how the page is structured and easily navigate between headings.
For an overview of this issue see Headings in our IT Accessibility Checklist.
In Canvas, headings are selected from the Blocks selector on the toolbar (by default, “Paragraph” is selected). Note that Canvas automatically uses Heading 1 for the title of the page, so the first heading available in the rich content editor is Heading 2 (see screenshot below). Therefore, all top-level headings in the main content should use Heading 2. If the page includes sub-headings, use Heading 3 or Heading 4 as needed, keeping in mind that headings should form an outline of the page content and should not skip levels.