iOS is Apple's most advanced and feature-rich proprietary mobile OS. It was released with the first generation of the iPhone. When introduced, it was named iPhone OS, and it was later renamed iOS to reflect the unified nature of the OS that powers all Apple iOS devices, such as the iPhone, iPod touch, iPad, and Apple TV. iOS is derived from core OS X technologies and is streamlined to be compact and efficient for mobile devices.

It utilizes a multi-touch interface, where simple gestures are used to operate and control the device, such as swiping your finger across the screen to move to the successive page or pinching your fingers to zoom. In simple terms, iOS assists with the general functioning of the device.