AMP (Accelerated Mobile Pages) is an initiative for improving the loading time of static mobile webpages. It specifies AMP HTML, which is a subset of HTML extended with some custom elements.

From https://www.ampproject.org/docs/get_started/about-amp.html:

AMP in action consists of three different parts:

  • AMP HTML
  • AMP JS
  • Google AMP Cache

AMP HTML is HTML with some restrictions for reliable performance and some extensions for building rich content beyond basic HTML. The AMP JS library ensures the fast rendering of AMP HTML pages. The Google AMP Cache (optionally) delivers the AMP HTML pages.