iOS 14.5 has brought an important update for Apple users, that is ensuring the privacy of users’ app data by preventing apps from accessing the IDFA or tracking advertiser on iPhones, iPads, or Apple TV without users’ express permission.
A pop-up will appear when an app wants to access your IDFA data. The message says "Allow [app] to track your activity across other companies' apps and websites?” You will be given two options: "Ask App Not to Track," and "Allow", that you can choose from.
There is also an option to avoid the pop-ups and block access to IDFA on all the apps at once. To do that, you need to visit privacy settings, tap on “Tracking”, and then toggle off "Allow Apps to Request to Track." As a result, you won’t be seeing tracking request pop-ups and no app will be able to access your IDFA data.
In case you want to turn the tracking option on for a certain app, but had the auto decline option turned on, you can turn it back off and then re-install the app.