supplemental content

additional content (opens in a new tab) that illustrates or clarifies the primary content

Example 1: An audio version of a web page (opens in a new tab).

Example 2: An illustration of a complex process (opens in a new tab).

Example 3: A paragraph summarizing the major outcomes and recommendations made in a research study.

Source: WCAG 2.2 definition of “supplemental content” (opens in a new tab) (W3C)