There are two sorts of rules: portal rules and upgrade rules.
The (portal page) rules determine what portal will be displayed to the client.
It is possible to have multiple rules. The portal page that a subscriber will see is depending on the sequence of the rules. You can change this sequence by clicking on the up/down arrow next to the rule name.
Upgrade rules are triggered when a client want to upgrade his current package. This happens when they enter the upgrade domain in their browser e.g. http://upgrade.com. The upgrade rules are identical to the standard rules but they only have the option to specify the billing packages. There is also an additional trigger, the current billing plan of the subscriber.
service → rules