The Partner Companies setting on the Configuration Options page allows you to list the usernames / registered email addresses of companies, which will be considered as partners and will be able to post jobs on the website without being charged for that.
It can be used also by the administrator to create additional accounts related to the admin one with possibility to post unlimited number of jobs on the website without passing through the buying a subscription first (if the subscription mode is enabled) or buying credits (if the credits option is active) or purchasing a job posting packages.
The user accounts / email addresses should be added one per line, for example:
user@somecompany.com
another_user@someothercompany.com
etc.