Health defines ones general vitality, whether it's ones immune system, pain tolerance, or physical body prowess. The lower ones Health is, the lower their HP will be.

Health may define your personal welfare, but if for example, someone else is in need of medical help: Health can be used to aid light wounds. It encapsulates both literal health, and the knowledge/skills that come with first-aid. A rarity in these days, as many people drop like flies.