The Articles panel and InDesign's new methods for mapping styles to PDF tags let you ensure content flows in the expected order when viewers use screen readers and other assistive technologies.
In previous releases, InDesign would export all block level text to a <p> tag and use CSS to create the visual presentation. A downside to this approach is that 3rd party applications could NOT infer any “semantic” meaning. For example, 3rd party accessibility readers could NOT read aloud text as a “heading” and EPUB readers with no support for CSS would present everything as a generic paragraph, since they could not find any “headings” in the code.
Users who needed more semantic markup had to use one or more of the following workarounds: