manifest_version: Specifies the version of the manifest file format. Version 3 is the latest and recommended version.name: The name of your extension as it will appear in the Chrome Web Store and in the extension list.version: The version of your extension, which must be updated with each new release.description: A short description of what your extension does.action: Defines the behavior of your extension's toolbar button, including the popup that will be displayed when clicked.permissions: Specifies the permissions your extension needs to function. Here, activeTab allows the extension to interact with the current tab.
Next, let's create the popup that will appear when the user clicks the extension's icon in the toolbar.