Strength is a Main Attribute.
Strength affects your primary combat capabilities. In addition to that, it increases the base Block Power, the Damage and Range for thrown items, and also improves unarmed Damage.
Each point of Strength grants +1.5% Block Chance and +2.5% Bodypart Damage.
Reaching a threshold of 15, 20, 25, and 30 points also grants:
+5% Weapon Damage
+7.5% Crit Efficiency
+10% Armor Damage
Strength is capped at 30 points.