Landing PagesA destination page for a link, such as a click of a Google ad, with a focus on ad content and a specific call to action. By nature, these pages need to load as fast as possible to discourage mobile visitors from abandoning the page before the message is read. This is particularly important when the page is called by a pay-per-click Ad where the advertiser pays for the click even if the slow loading landing page is abandoned before the message is read.
Companion PagesThese are specialized landing pages, mirroring a page on a conventional website, constructed using Accelerate Mobile Pages (AMP) technology to take advantage of Google's AMP cache to provide almost instant delivery to a mobile search user. Both the original website page and mirrored page have a specialized link to each other advise Google of the duplicate content they contain. The original page, the one being mirrored, will have an "amphtml" link to the mirroring AMP page. The AMP page will have a canonical link back to the page it is mirroring.
The Google Cache, AMP Landing Pages, and AMP Companion PagesWhen the Google robot crawls a website and encounters a page with an "amphtml" link it follows the link, and if the page it finds is a valid AMP page, the robot copies the AMP page content directly into the Google cache to be used later for instant delivery as a search result to a mobile searcher. The URL displayed in the address bar of the browser is that of the original (canonical) page. The original page is also cataloged and delivered with normal search results when the searcher is using a non-mobile device.
Stand-alone AMP pages have a canonical link to themselves so they are added to the Google AMP cache and treated like regular web pages for inclusion in standard search results.