If you were to divide everything that makes up a computer and its software into what the average user interacts with, and everything else that works "behind the scenes", what would the "user-part" be called? What would the "behind the scenes" part be called?
For example, on my Windows laptop I'd consider things like the desktop, taskbar, and File Explorer "user-parts" and things like the command prompt or the BIOS as "behind the scenes". On a website, the HTML code would be "behind the scenes" and the visuals, text, etc. that the code produces would be the "user-part".