"We've heard from some customers that it was too easy for their kids to make in-app purchases. As a result, we've improved controls for parents so they can better manage their children's purchases, or restrict them entirely. Additionally, we are offering refunds in certain cases," Apple states in the email.
To request a refund, you'll need to dig up the order number, which you can find by sifting through your archived emails (Apple sends a receipt for in-app purchases) or by launching iTunes and looking up your Purchase History. Once you have that information, head here and click on the Email icon. Fill out the form that appears, including the order number you retrieved, and give your reason for requesting a refund -- "Seeking refund for unauthorized in-app purchase made by a minor," or something to that effect.
This all started when the FTC filed a complaint saying that Apple didn't inform parents that by sharing a password to approve an in-app purchase, minors could make unlimited purchases for up to 15 minutes. According to the FTC's complaint, Apple received tens of thousands complaints related to unauthorized charges by minors, some of which totaled thousands of dollars.
Apple settled the lawsuit by agreeing to refund all unauthorized payments to customers. The FTC estimates the refunds should add up to at least $32.5 million, though it could be a lot more. If it ends up being short of $32.5 million, the FTC will collect the difference.