iCloud: iOS software version
iOS is the mobile operating system for the iPhone, iPad, and iPod touch. For best performance, it’s a good idea to update all iOS software on your iPhone, iPad, or iPod touch to the latest versions.
To determine which iOS software your device uses, go to Settings > General > About > Version.
To update the iOS, connect your device to your computer and install the latest iOS using iTunes.
You can install future updates from your device by tapping Settings > General > Software Update.