How to make sense of a PCB in electrical circuit terms,
&quot;Reading&quot; a PCB is a learned skill that can really only be acquired by doing. Nobody can really tell you how to reverse-engineer it, you have to learn that on your own. Usually the best way to learn it is to design PCBs for yourself and understand why components are laid out in a certain way and how they are routed to each other. It is often a long-drawn out process for anything but the simplest of boards.
I recently reverse-engineered a LAN/VGA module created by Keysight to connect their 3000X series scopes to an external VGA monitor. I documented the process here:
https://www.eevblog.com/forum/projects/dsfauxlan-reverse-engineering-the-agilentkeysight-dsoxlan-lanvga-modul-220158/msg2805820/#msg2805820
Parts of it I was able to determine by inspection, but other parts I had to brute-force. I had to probe out many of the component pins and vias manually using the continuity test on my multimeter in order to figure out where they were connected. If I didn't do PCB layout for a living, I'm not really sure how I would have done this. Having an understanding of how PCBs are designed, manufactured, and assembled was absolutely crucial.