This access code makes it possible to prohibit access to the current record for some users.
If the field is populated, only users that have this access code with read access rights (and write access rights respectively) can view (or with write access rights, modify) the record.
This access code makes it possible to prohibit access to the code for certain users.
If the field is assigned, only those users who have this access code in their profile can modify and/or enter this code according to the rights accorded.