Will is a saving throw in Pathfinder: Wrath of the Righteous.
Your Will reflects your resistance to mental influence as well as many magical effects.
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 Wisdom modifier is added to your Will saving throws.