Higher Item Discovery determines the likelihood of an enemy dropping an item such as a weapon, an upgrade material, or consumable item.
As with normal weapons, there is a scaling mechanic. A letter denoting a weapon's specific scaling properties is noted beneath the weapon's required stats. The range, in order of effectiveness, from lowest to highest is denoted by the letters: E, D, C, B, A, and S.
As is with every other stat in the game, it also has indirect bonuses such as increasing the player character's flat damage absorption.