For iOS the authoritative source is apple itself; you can read their post on this topic here: https://support.apple.com/en-us/HT211970

The actual list of privacy descriptors and what they actually mean can be found here: https://apps.apple.com/story/id1539235847

For example, the description of “Health and fitness” is:

> Health and fitness

> Health

> Health and medical data, including but not limited to information from the Clinical Health Records API, HealthKit API, and Movement Disorder API, or from health-related human subject research or any other health or medical data that you provide.

> Fitness

> Fitness and exercise data.

Which indicates that the app can use HealthKit etc to gather information about your health and medical data and exercise data.