Protecting your privacy
Apple has made privacy a high priority in recent years and this update is no exception. There are a number of privacy measures in iOS 15 besides those in iCloud+. Mail Privacy Protection hides your IP address so senders can’t see your location or link it to other activity. And senders are preventing from seeing whether you have opened a message.
App Privacy reports enable you to see how apps are using the permissions you have granted them and also which third-party domains they contact. You can also see how recently they’ve contacted those domains.
And on-device audio processing in Siri (if you have an iPhone with an A12 Bionic chip or later) means that the audio never leaves your device.