The maintenance task runs on all the AODocs libraries on your domain. It checks that all documents and folders in your libraries have a parent folder that belongs to AODocs.
If it finds any documents or folders that don't have a parent folder, it creates the lost+found folder and restores the orphan documents and folders to this folder.
Note: Normally, there shouldn't be any documents or folders whose parent folder can't be identified. However, this may occur in rare circumstances when there is a problem in Google Drive or AODocs when performing a move, delete or restore operation.
Contact your library administrator if you don't know what to do with the documents and folders in the lost+found folder.