A language that uses a set of annotations or tags, which instruct how text is to be displayed. On the web, HTML is the most commonly known markup language, and uses tags to instruct web browsers how to display web pages. Other markup languages in use on the web include XML and XHTML.
A meta description is an HTML header tag that allows a web author to describe the contents of their HTML pages. Search engines often use meta descriptions to describe pages to their search users.
A concise and descriptive meta description will encourage more search users to visit your page in their search results, making quality meta descriptions very important to SEO.