iOS vs iPadOS

1. They're different names for the same OS.

2. Which name Apple uses depends on the unit and current version; there's only one for a specific configuration.

3. It's iPadOS in version 13 or newer on an iPad. Otherwise, it's iOS.

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Expanding upon Niel’s summary, up to and including iOS12, the differences between iOS for iPhone and iPad were relatively minor.

However, from iOS/iPadOS13, whilst iOS and iPadOS remain closely related, iPadOS differentiates from iOS in several significant features - in particular multi-tasking on iPad. These advanced features require the newer CPU/GPU derivatives that are optimised for iPad.

Apple has indicated that the iPadOS “fork” (a computing term that describes a divergence) will continue to incorporate more features that can be successfully implemented on large-format devices. As such, over time, we are likely to see greater differences between the iOS and iPadOS feature sets.