Hero skills influence your resource production, attack, defense, and troop life. Once unlocked, the buff will be available for all your heroes in the great hall, in all your available cities.
However, unlocking skills will not automatically add the boost to your account. In order to activate a skill, you will need to enroll it.
How do I unlock hero skills?
You can unlock these special boosts with skill points.
For more info, check out [this] forum post.