The document role - ARIA Reference Guide

Composites
Represent containers for navigating interactive descendants.
Landmarks
Represent top-level sections of a page, relevant to a specific purpose, that a user may want to scan for quickly and could appear in a site map or table of contents.
Live Regions
Represent dynamic content or announcements, typically updated as a result of an external event when user focus may be elsewhere.
Structures
Represent non-interactive parts of a page that organize content into coherent units.
Widgets
Represent focusable, interactive elements.
Windows
Represent inner windows that are children of the main web document.

Description

An element containing content that assistive technology users may want to browse in a reading mode.

Flow content

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