Apple Inc. uses the denotation "iOS" for the operating systems installed on all of their mobile devices. This includes the iPhone, iPad, and iPod Touch. Mobile operating systems run applications or "apps" rather than programs, which necessitates an entirely new programming language separate than that used for desktop technology.
Although iOS is the name of the operating systems for mobile devices, desktop machines run on the OS X platform. The operating system is in charge of managing all of the computer's software (the programs you run) and the hardware (the physical components of the computer such as keyboard, mouse, cooling fans and hard drives). When Apple Inc. was originally founded, the lowercase "i" stood for "Internet." This was because an Internet connection used to be difficult to set up, and Apple's profound technology turned it into a simple process. Originally, Steve Jobs, the inventor of Apple Inc., wanted to name their new computer "MacMan," but he was eventually convinced to settle on iMac as a more revolutionary namesake: the "i" standing for the "individuality" and "innovation."
Ever since, the prefix was adopted for all Apple products: hardware such as iPods, iPads and iPhones, and software such as the iLife suite, iWork, and iTunes.