Answer Description

iOS is Apple's operating system for their mobile devices (iPhone, iPad, iPod Touch). IOS can also refer to Cisco's Internetwork OS, but not typically from a user.

Wikipedia

iOS (formerly iPhone OS) is a mobile operating system developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes the system software for iPads predating iPadOS—which was introduced in 2019—as well as on the iPod Touch devices—which were discontinued in mid-2022. It is the world's second-most widely installed mobile operating system, after Android. It is the basis for three other operating systems made by Apple: iPadOS, tvOS, and watchOS. It is proprietary software, although some parts of it are open source under the Apple Public Source License and other licenses.Unveiled in 2007 for the first-generation iPhone, iOS has since been extended to support other Apple devices such as the iPod Touch (September 2007) and the iPad (introduced: January 2010; availability: April 2010). As of March 2018, Apple's App Store contains more than 2.1 million iOS applications, 1 million of which are native for iPads. These mobile apps have collectively been downloaded more than 130 billion times. Major versions of iOS are released annually. The current stable version, iOS 16, was released to the public on September 12, 2022.