Put simply, iOS is a condensed way of saying ‘iPhone OS’, or ‘iPhone Operating System’.
iOS is the mobile operating system that runs on Apple’s mobile devices. It’s the core software that lets you interact with your Apple phone or tablet.
Critically, iOS also allows you to run any aplications that you download from the App Store. While your apps are running, iOS does all the hard work, managing your iPhone or iPad’s memory to ensure that the device runs efficiently.
Apple is continuously updating iOS, to add new features to your device, or simply improve the experience by modifying existing apps and eliminating any bugs.