When authentication is required, users must log in to access the portal.
By default, authentication is not required. To require authentication for a tenant, select the check box in the Mandatory authentication section of the Authentication administration interface.
The administrators of a Fluid topics portal have configured content access rights to restrict content to authenticated users only. If authentication is not mandatory, unauthenticated users can still access the portal and may be confused when it appears empty. Requiring authentication addresses this issue.
Making it mandatory for users to authenticate does not prevent bots (or anyone pretending to be a bot) from accessing public content. The only way to protect content from being crawled and indexed (and thus made accessible) is to configure content access rules.