Personal data can be any kind of information that identifies an individual:
The Federal Trade Commission in the United States, requires all the applications to collect and make use of personal data from different users to well inform about the collection of users’ personal data.
The FTC also provides guidance for the businesses and developers on the things to be aware of for ensuring compliance.
This particular requirement relates to all the app stores, including Android and iOS:
Depending on the mobile app and the genre of business, you might also need to know about the other legal requirements necessary for your app: