A subscription is a mechanism to make an app (and so services offered by the app) to function smoothly, without any interruption. Mechanism of app subscription is provided by Apple - and used by apps. Apple manages and collects payment from subscriber’s Apple ID - and the payment method associated with it. The subscription renews automatically once the user gives initial consent. It is the app that offers a subscription plan with different renewal (and so payment) frequencies like - weekly, monthly, and yearly.