Strength, STR in your 'score', represents your character's physical power.
The most common concern with strength deals with how much your character can carry. For each additional point of strength, you gain an additional amount of maximum carryable weight. Any character with 20 strength can carry 500 kgs. Any character with 25 strength can carry 999 kgs.
Among other things, strength affects:
Strength is the prime attribute of the Warrior, Ranger, and Paladin.
*Information as of July 27, 2005