In practice, the new iOS privacy feature lets users decide whether they want to allow apps access to their Identifier for Advertisers (IDFA) tag. Apps that continue to track users even when their users have opted out of the tracking, reportedly run the risk of being evicted from the App Store.
Tech Tip: Choose whether to let apps track you in iOS 14.5
You can now choose whether to let apps track you in iPhone’s iOS 14.5. And only 13% of people have said “yes." Apple's app tracking transparency tool (ATT) makes apps seek permission from users before tracking their data across other apps or websites usually for advertising purposes.