|Apple has added a "Learn More About In-App Purchases" section to the App Store, AppAdvice observes. Tapping on the option explains what in-app purchases do, and the way the in-app purchase scheme works, specifically pointing out that while an Apple ID password is needed for an initial purchase, a 15-minute window exists during which more things can be bought without re-authorizing. Apple also places an emphasis on the Parental Controls menu under Settings, where people can turn off access to in-app purchases entirely.
The guide was probably added in response to a number of complaints, legal and otherwise, about children racking up hundreds or thousands of dollars on their parents' credit card bills. Many iOS children's games are only superficially free, in truth requiring in-app purchases to make significant progress. In some cases apps have been accused of hiding the fact that real-world money is being spent, fooling both kids and parents.
Apple only recently began adding "Offers In-App Purchases" labels to App Store pages. The effect of the new guide may be limited, as it has so far only been spotted on the iPad version of the App Store, not the iPhone or desktop storefronts.