Nevermind. I see that those are all in the USER table.
Primary, Secondary, Tertiary are only for user notifications. You'll notice they don't show up when emailing other values (such as address book).
When configuring users, you need to configure a Primary email, and by default it is checked to notify on that one:
Your business rule can then be configured to notify a specific address (primary, secondary, or tertiary), or whatever notification setting the user has:
Users in their preferences can then manage their email addresses and notification preferences if your rules are configured to do that: