The criteria of a rule can be made complex by configuring it with two or more parts.
In complex criteria, each of the parts has a property with operator and operand. The parts are linked by AND or OR.
The criteria is matched if a filtered URL belongs to a category that is on any of the two specified category lists (or on both).
If you configure criteria with three or more parts and use both AND and OR between them, you also need to put brackets to indicate how the parts are logically connected. For example, (a AND b) OR c differs in meaning from AND (b OR c).
When you add a third criteria part on the user interface, lowercase letters appear before the parts and an additional field is inserted at the bottom of the configuration window.
The field displays your criteria parts in short, for example, a AND b OR c. You can then type brackets in the field as needed.