In sustainability reports there may be one or more auditors of a report and each may audit a number of different items.
Sometimes the audit is of the whole document, sometimes at the level of a specific fact and sometimes in between, a section/page/table is marked as audited by a particular audit firm.
There needs to be a way to see clearly what has been audited and who has audited it.
Example
An example of a fact that is marked as unaudited:

An example of a fact capturing details of the auditor
(note the different LEI) and the “Associated facts” that are audited:

An example of a fact that is marked as Audited is below. You can see that the link can be followed in either direction (from the auditor to the audited facts or from an audited fact to
the auditor fact)

Links
An example inline XBRL filing with audited and unaudited facts that have links to the other facts in the filing to show whether those other facts are audited or unaudited:
Inline Viewer – CarMaker Sustainability Disclosure (xbrl.org)