Schema.org (often called Schema) provides a collection of shared vocabulary of tags (or microdata) that you can add to the HTML code of your web pages (markup) so that they can be understood by the major search engines: Google, Yahoo, Bing, etc and also improve the way your pages are represented on search engine results pages (SERPs).
Sounds fairly complicated, I know, but its really not...
Ever wonder what the little lightning bolt icon means when you do a Google search on your mobile device? These are AMP or "Accelerated Mobile Pages". As internet use continues to shift toward mobile use, it becomes more and more important to address these users. Its now estimated that more than half of web traffic is mobile. Additionally, Google has been increasing the importance of pagespeed, or page load time, in its search result ranking algorithm.
You can see for yourself what % of your site's traffic is mobile in your Google Analytics reports.