The banner 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

A landmark that contains mostly site-oriented content, rather than page-specific content.

Flow content but with no main, header, or footer element descendants.