Reflex is a saving throw in Pathfinder: Wrath of the Righteous.
To prove your ability to dodge area attacks and unexpected situations, you must roll a successful Reflex saving throw.
Generally, when you are subject to an unusual or magical attack, you get a saving throw to avoid or reduce the effect. Like an attack roll, a saving throw is a d20 roll plus a bonus based on your class and level, and associated ability. Your Dexterity modifier is added to your Reflex saving throws.