
Touch ID is a super convenient way to unlock your iPhone 5s while keeping it secure at the same time. You can also use it to make App Store and iTunes purchases by default. However, if you've registered other family member's prints and you don't want them to be able to buy things on your account, or if you're just not comfortable with Touch ID purchases, you turn off iTunes purchases and not have to worry about it.
Full story from the iMore Blog...