The document introduces Web Components and promotes trying them. It provides examples of Web Components like <x-calendar> and <x-flipbox> that can be used to build reusable custom elements. It also describes how to create a Web Component using Polymer and shows an example <x-like> component for liking posts. The document encourages developing with Web Components as it makes front-end development more fun and modular.
10. <x-flipbox>
<div>I'm the front face.</div>
<div>And I'm the back face.</div>
</x-flipbox>
http://mozilla.github.io/brick/demos/x-tag-flipbox/index.html