Apple announced iOS 15 at WWDC 2021, the new iOS is coming later this year with the new iPhone 13 smartphones.
When Apple releases a new version of iOS, you will need to update your device to that update in order to get the latest security updates, things will be changed with iOS 15.
When iOS 15 is available to the users, Apple will give you the option to upgrade to the software, or stay on iOS 14 and still get security updates,
iOS now offers a choice between two software update versions in the Settings app. You can update to the latest version of iOS 15 as soon as it’s released for the latest features and most complete set of security updates. Or continue on iOS 14 and still get important security updates until you’re ready to upgrade to the next major version.
This could be a valuable feature if you do not want to upgrade to the new iOS and you can have it when you want and not be forced to update to get the security updates, it will be exciting to see how this thing works when the next iOS is released.