Chrome extensions are just web pages with superpowers — but the superpowers come with rules. This is the beginner's map: the parts, the permissions, why your popup can't see the page you're looking at, and the caveats that bite everyone exactly once.
You built the extension and it works with "Load unpacked". This is the map of everything between that and a public Chrome Web Store listing: the one-time $5 fee, the images the listing needs, the privacy paperwork, the review, and the maintenance that never quite ends.