message: docs: add universal terms to glossary
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diff: @@ -40,6 +40,19 @@ Learn more in [Angular Elements Overview](guide/elements).
  A structure that provides metadata for a class. See [decorator](guide/glossary#decorator).
  +{@a app-shell}
  +
  +## app-shell
  +
  +App shell is a way to render a portion of your application via a route at build time.
  +This gives users a meaningful first paint of your application that appears quickly because the browser can render static HTML and CSS without the need to initialize JavaScript.
  +
  +Learn more in [The App Shell Model](https://developers.google.com/web/fundamentals/architecture/app-shell).
  +
  +You can use the Angular CLI to [generate](cli/generate#appshell) an app shell.
  +This can improve the user experience by quickly launching a static rendered page (a skeleton common to all pages) while the browser downloads the full client version and switches to it automatically after the code loads.
  +
  +See also [Service Worker and PWA](guide/service-worker-intro).
  {@a attribute-directive}
  @@ -701,6 +714,19 @@ Import a scoped package in the same way that you import a normal package.
  </code-example>
  +{@a server-side-rendering}
  +
  +## server-side rendering
  +
  +A technique that generates static application pages on the server, and can generate and serve those pages in response to requests from browsers.
  +It can also pre-generate pages as HTML files that you serve later.
  +
  +This technique can improve performance on mobile and low-powered devices and improve the user experience by showing a static first page quickly while the client-side app is loading.
  +The static version can also make your app more visible to web crawlers.
  +
  +You can easily prepare an app for server-side rendering by using the [CLI](guide/glossary#cli) to run the [Angular Universal](#universal) tool, using the `@nguniversal/express-engine` [schematic](#schematic).
  +
  +
  {@a service}
  ## service
  @@ -810,6 +836,16 @@ Read more about TypeScript at [typescriptlang.org](http://www.typescriptlang.org
  {@a U}
  +{@a universal}
  +
  +## Universal
  +
  +A tool for implementing [server-side rendering](#server-side-rendering) of an Angular application.
  +When integrated with an app, Universal generates and serves static pages on the server in response to requests from browsers.
  +The initial static page serves as a fast-loading placeholder while the full application is being prepared for normal execution in the browser.
  +
  +To learn more, see [Angular Universal: server-side rendering](guide/universal).
  +
  {@a V}
  {@a view}
  