CiviCRM has the ability to automatically grant memberships to related contacts. So, for example, when a company purchases a membership, employees of this company can be automatically extended the same membership. In the user interface, these memberships are then flagged as ‘by relationship’.
But up to today this was an all-or-nothing proposition: all employees of the company where automatically granted a membership, with no ability to neither limit the number of related memberships, nor choose which of the employees would get these.