Apple's Health app for iPhone debuted with iOS 8. Health provides a central place for all your medical, fitness, nutrition, sleep, and related information.
Categories include Diagnostics, Fitness, Lab Results, Me, Medication, Nutrition, Sleep, and Vital Signs. Data is presented in both graphs — which can be added to the dashboard view — and in separate sub-catagories. Once the information is collected, you can either keep it just for yourself, or you can choose to send it to other apps, or even share it with your medical professional via Apple's HealthKit framework. There's even a medical ID feature to help responders to find out vital information in case of emergency.
Privacy is a huge emphasis for Health, and you can control not only the data you collect, and not only which apps can access that data, but which apps can read it and which apps can write it. And if you don't give permission, an app — and any insurance or health organization behind it — doesn't even know it's there.
That's what Health is, but what do you want Health to be?