The File System – Approve File functional permission is available when configuring user groups in the User Groups configuration interface.
It is used to grant to users the ability to approve files. If a user is a member of a user group associated with the functional permission, and that user group is in turn associated with the file type approval record for a given file type, then that user is deemed to be an approver for the file type in question. He or she may approve files of that type and deny approval in respect of the same.
Note that the ability to request approval of a file is not controlled by this functional permission, being open to all RPI users.