Basically, you can use C ++ / C # to create IOS, Android and Windows applications and use Shared project to share class library between platforms, it is a solution that builds several different binaries, one for each operating system.
To understand how it does this you have to understand how the compilation is, briefly you are transforming a strongly abstract code into a code closer to the machine language, however that generated object code is natively created for an operating system. Formerly the compiler only generated codes for the Windows operating system, now it can create different binaries for Android and IOS as well.
This last question did not find anything concrete, but it is very likely that he is using Xamarin technology to do.
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