Aim has a highly notable influence on your offense. Every point Aim gives +8 points in offense calculation (which means a char with 50 Aim will have 320 offense rating more then a char with 10 Aim).
Thanks to this high Aim chars will hit way more often then low aim chars.
Aim offers bonus damage to attacks made with Thrust Weapons and Bows. This damage is an additional percentage of base damage.
The bonus is 1% per 1 point of Aim, within a certain range of the stat.
The percentage bonus begins at 25 Aim, and ends at 65 Aim. Examples:
Yang the Barbarian swings a Short Sword, which rolls a strike of 10 damage. He is fully proficient, so he gains 5 base damage, for a total of 15. He has 45 Aim, so his base damage is multiplied by 1.20, a gain of 20%. His final base damage is 18.
Thereafter, he gains 3 points of damage from his personal Bless buff, which gives an additive bonus. His attack lands, attempting to deal 21 damage.
The creature Yang is fighting is 25% resistant to thrust damage and is wearing weak armor. That creature receives the 21 damage, which is reduced to 20 by the weak generic armor. That 20 damage is then reduced to 15 by his 25% thrust resistance.
Yang deals 15 damage, and shouts with exuberant joy as his target crumples into a heap of loot.