At what point do you say "You know what, a beginner should know this"? Or whatever the specific level you decide to teach at.
Personally I try to teach at levels above beginner. This only makes the line blurrier because there's no clear divide between someone who kinda knows his stuff and someone who's an expert. It's the same problem as putting rocks in the same place. At what point does a bunch of rocks become a pile?
Same here, at what point does a total beginner become just a beginner? When do they become not a beginner? What turns them into someone who kinda knows what they're doing? At what point do they become "actually kinda good"?
For instance: my mum can accomplish all her work tasks with a computer. But she has no conceptual idea of what is a file. She thinks in documents and she only knows how to open documents by going through the app she created them with. The attachments in her email are a completely different world than the ones she creates with Word directly. I once blew her mind by showing her that she can use Word to open something that was sent to her via email.
Or, for another example, my girlfriend always gets frustrated with me because I can't just "Explain How Everything in Computers Works. How Does a Source File Turn Into A Working App?" in under five minutes. How do you even begin answering a question like that? Do I claim magic, or start with turing machines and work her way up to formal grammars and compilers? She's asking a question so far beyond her understanding that I don't even know how to begin answering.
You could try to be romantic and playful and say the love child created by a sexy, error-free relationship between source code and the compiler is an executable?
Sure, they (probably) understand what a file is much better than your mum, but still: Canvas, "this", libraries, dependencies, etc etc..
I was having trouble explaining stuff to my father as well but I realised that I don't have to give him a pretty picture of how a computer works when all he wants is to be able to reply to emails, print attachments and create documents. Forget the file system and the desktop and the folders and this and that, all he wanted was simple step guides to perform these very specific tasks.
In the end, the teaching process is the same, no matter how (non) beginner someone is: There is always something they probably don't know and you don't have to teach them the whole universe before they learn how to do something. You don't have to know what electricity is in order turn the lights on..