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 created and 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 and iPod Touch it also powered the iPad until the introduction of iPadOS, a derivative of iOS, in 2019 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
IOS - Wikipedia, the free encyclopedia