AMP Extensions are either extended components or extended templates.
Extended components must be explicitly included into the document as custom elements.
For example, to include a YouTube video in your page
include the following script in the <head>:
<script async custom-element="amp-youtube" src="https://cdn.ampproject.org/v0/amp-youtube-0.1.js"></script>See the Components list.
See the AMP template spec for details about supported templates.