What is schema markup?

Schema markup is an advanced SEO approach that gives search engines context of the website content, using a semantic vocabulary categorized on Schema.org, and paves way for the content to be displayed as rich results on SERPs. In 2011, the Big Four search engines at that point-Google, Yahoo, Bing and Yandex-collaborated to create Schema.org in order to classify and categorize entities online in the form of microdata or tags which came to be known as schema markup.