The article describes it pretty well. If it's still not resonating, I know it might come off disingenuous but really I would suggest pasting the description from the article into chatgpt and asking it to describe it to a "lowly systems guy" as you refer to yourself.
"Design system: A complete set of standards and principles to manage design at scale. It can include, but isn’t limited to, the visual design language, typography, colour palettes, components, copywriting guidelines, and other elements that create a cohesive, scalable look and feel for the product."
