Strength is one of the core attributes for characters in Diablo III. It governs how much Armor a character has and increases Barbarian's damage dealt.
Each point of Strength gives:
Before the first attribute changes in 2010, Strength was one of the core stats, just as it was in Diablo I and Diablo II.
Strength governed a character's damage, armor rating, and blocking percentage.
1 point of Strength gave: (based on Class)
Strength was replaced with Attack in 2010's attribute changes.
After the second attribute overhaul in 2012, Strength made a comeback, replacing Attack as one of the core attributes.