The manifest file is a JSON file. Here we list the name, description, icons, and manifest version--among other things--of our Chrome extension. For this tutorial, we're working with manifest version 3; think of it like the software version. In here we define where our background, popup, and options components are located in our file directory. Notice I didn't include the foreground location here. There are two ways of including the foreground script in a Chrome extension: through the manifest (which we won't do in this tutorial) and programmatically (which we will do in this tutorial).
From below, background.js is a kind of the mainframe or hub of a Chrome extension - it works like a backend environment.
{ "name": "Chrome Extension MV3", "description": "Learning all about Chrome Extensions Manifest Version 3!", "version": "0.1.0", "manifest_version": 3, "icons": { "16": "/images/icon-16x16.png", "32": "/images/icon-32x32.png", "48": "/images/icon-48x48.png", "128": "/images/icon-128x128.png" }, "background": { "service_worker": "background.js" }, "action": { "default_popup": "popup.html", "default_icon": { "16": "/images/icon-16x16.png", "32": "/images/icon-32x32.png", "48": "/images/icon-48x48.png", "128": "/images/icon-128x128.png" } }, "options_page": "options.html", "permissions": [ "storage", "activeTab", "scripting", "tabs" ], "host_permissions": [ "https://www.google.com/*" ] }