Ask to Buy funnels all requests for app or media content purchases to the Family Organizer, and anyone else they have designated as a Parent/Guardian, to approve the purchase. For a paid app or media content, once approved it is bought with the credit card designed by the Family Organizer.
When setting up Family Sharing, all Apple IDs which have an age of 13 or less automatically have Ask to Buy enabled for them. When inviting those aged 13 to 17, iOS prompts you to enable Ask to Buy.
Once enabled, the Family Organizer can later disable it for each individual. If their account reflects that they are over 18 when it is disabled, it cannot be reenabled for that account. Similarly, Ask to Buy is not even an option for users who are invited after they turn 18.
In your case, your ID is set up for Ask to Buy. You can give your Family Organizer a link to the Ask to Buy Apple Support page for details on how to disable it. It has to be done from their device.
Free apps are included in Ask to Buy for two reasons:
- Ask to Buy is not just about the cost of the purchase, it is also about parental review of the content of the app/media content
- Free apps can (and often do) still have in-app purchases, though an Ask to Buy user attempting to do this will still have to get permission to complete the in-app purchase