Not everyone has a credit card or wants to use it for online payments. In that case, there is PayPal to deviate from. You can now also use this service for all your iTunes and app store accounts in iOS. Paying with PayPal in iTunes is something you do.
Paying for music, movies, and apps on your iPhone, iPad or iPod Touch could only be done by credit card for years. Annoying, because you always have to make sure that you manually return the debited amounts to prevent a deep red card. You also pay for the use of the card and so on. One solution was to buy iTunes gift cards in the store and to redeem their value with apps and more. For a while - probably after a lot of whining of users - can also be paid through PayPal. This is a payment service that you can link directly to (for example) your bank account. A payment made via PayPal is automatically debited from your regular bank account. No more hassle with a mandatory credit card!
To make your i-devices in order for payment via PayPal you start the Settings app. Tap in the column with options at the top of your (account) name. Then tap Payment and delivery. In a new panel again, tap Payment method on the method selected there. That will - if you have never looked at this before - be a credit card. Then choose PayPal
If you are going to use PayPal, it is, of course, important to close this service with a very strong password. If you do not do that and your account is hacked, the turnips are done. Use a good password generator, such as this online copy. And save your passwords in a well-secured password manager, such as mSecure for example. So you only have to remember one password to access all those un-remembered random passwords. Is that all right, then you pay all your iTunes purchases completely worry-free via PayPal.