Healthkit is a platform launched by Apple as part of iOS 8 that allows health and fitness apps to share data. The Health app acts as an interface for this data, allowing users to view all health data from various sources in one place. It provides summaries of metrics over time and categorizes data types such as fitness, nutrition, vitals, etc. Apple partners with organizations to integrate health records and is exploring potential for the Apple Watch to monitor more advanced health data. Healthkit aims to simplify health data tracking and sharing across apps and devices.