Thank you for contacting the Instructure Community. Your screenshot sort of explains it - If you use an SSO/SAML - it is information sent from your authentication provider that will be used automatically each time a user logs in. For example, if you used Google or Microsoft as your authentication provider - having the admin_role tells Canvas that this person has admin permissions each time you login and you will have access to all things admin_role would get. Students would be recognized as students, teachers as teachers, etc. It's essentially just passing back that information automatically showing that you are an admin. Here is the Canvas guide that explains it a little more:
How do I configure third-party authentication prov... - Instructure Community .
Hopefully this helps.