Is my App a Reader App?

I understand that in IOs and Android if your App is consider a reader App you can direct user outside the App store to get a subscription?

1. Do this reader classification exists?
2. What characteristics do reader Apps have to have?
3. Taking into account the terms from the Apple and Android store, can I take this users from an 'Reader App' and direct them to a Stripe base payment?

Thank you,