Aha! That makes your question make sense. I haven’t used or even read it and don’t know whether it’s up to date, but you may want to start at https://developer.

Aha! That makes your question make sense. I haven’t used or even read it and don’t know whether it’s up to date, but you may want to start at https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/OSX_Technology_Overview/About/About.html https://developer.apple.com/library/archive/documentation/Ma..., and then, probably, click the “Kernel and Device Drivers Layer”. That, at least, should get you an idea about the terminology.