FAQ About The iOS
There was no official name for the iOS until March 6, 2008, when the official iPhone software development kit (iPhone SDK) was released. Apple marketing team simply stated that iPhone ran a version of Mac OS X that was made specifically for the iPhone. It was called iPhone OS when it was first introduced.
The iOS is only available to Apple devices and products, the apps marketplace for the iOS is known as the App Store which is different from the Google Playstore.