In Mad World: Age of Darkness your character has four different attributes: Attack (ATK), Defense (DEF), Physical (PHY) and Spirit (Mind).
Every time you gain a new level, you gain 6 attribute points to freely distribute among these attributes.
Attack (ATK)
Each point spent increases Attack by 1 and all Elemental Resistance Penetration by X.
Defense (DEF)
Each point spent increases Defense by 1 and reduces all Elemental Resistance Penetration by X.
Physical (PHY)
Each point increases HP by 5 and HP Recovery when using Potions(?) by X.
Spirit (Mind)
Each point increases MP by 5 and MP Recovery when using Potions(?) by X.
Some items provide attribute points. There is a difference between ability boosts and bonuses. An ability boost is actually being added to your attribute points while a bonus is just raising the calculated value e.g. DEF Ability Boost +8 will raise your actual DEF attribute while DEF Bonus +8 will just raise your calculated Defense value.