Each attack targets one of five possible Defenses: Parry, Dodge, Endurance, Will, or Magic. Enemies and party members have different strengths and weaknesses in these defenses, making some attacks better options against one type of enemy than another.
Accuracy is compared to Defense, and the resulting difference is used to modify the combat result table. Higher Accuracy results in a greater chance to Crit or Hit, reducing the chance to Graze or Miss. A lower Accuracy has the opposite effect, making you Graze or Miss more often.