TwoTrees Sapphire Plus - 3D Printer Motherboard Concepts and Operation for Idiots?

So, I'm on a quest now. Elsewhere, in the Hardware section, I'm carrying on a discussion to get my printer working. But, I'm also trying to understand in the bigger picture how all of the parts come together. I know, for example, that the motherboard in the printer has "cheatsheet" that identifies all of the pins on the mboard. Somewhere, there is a file that ties those pins to a printer function. And so on and so on until we get to some Gcode, telling the printer to do something. I'm trying to understand how those pieces fit together, and how I'm supposed to manage them in terms of setting up parameters and such. What files do I need to do what? What needs to be compiled? How do you get those things back into the printer? Is there documentation that anyone is aware of that ties these pieces together? Part of this, I suppose, is more generic than a printer. It's more about how hardware and software work together to do things. And that's what I'm trying to understand. I've been doing a good deal of looking around, and I've found a good deal of information, but not quite what I think I need, yet. So, has anyone seen information that explains how this works? Someone was kind enough to share some information on Marlin, and it's very helpful but not quite "there" yet. Any pointers would be appreciated.Thanks.Ron