Your Apple ID is used whenever you want to make purchases from one of Apple's online digital content stores. This includes the App Store, Books Store, and iTunes Store.
From time to time, you may switch credit card providers, get a new credit card number, or opt to use a different payment method than the one you're already using.
It's easy to change your Apple ID payment information right from your iPhone, iPod touch, or iPad and in this tutorial, our aim is to teach you how.