Many thanks to @timkaye @EliteStarServices and @Web242 for the informative and helpful responses; I appreciate your taking the time to help me sort through this thing. I also found the brief remark from @ElisabettaCarrara helfpul in the topic on Word Fence, namely
First layer is the server, second is the code, third is the admin and their behavior, fourth is the eventual user/site visitor and lastly the devices involved in managing/visiting the site.
@EliteStarServices Your overview is worth considerably more than 2 cents; many thanks.