The Accessibility section contains the Known Problems Report and the Likely Problems Report, which show the known and likely accessibility issues across the entire site, measured by the accessibility standard that is defined from Account Settings in the Setup menu.
Known problems are issues with the page HTML that are verified to be currently causing an accessibility issue. Each known problem will be listed in its own box and will show the specific Problem, the Repair for that issue, and the list of offending pages. The list of pages contains links that allow users to travel to that page and edit it, and to travel to that page's Page Report within Insights.
Clicking the Problem will bring up an external link that gives more detailed information about the issue.
Likely problems are issues that commonly cause accessibility problems. Each likely problem will also be listed in its own box, showing the Problem, Repair, and list of affected pages.
If you have accessibility check exceptions configured for your account, they will not appear in the Insights report.