Meta tag is a coding declaration in the Hypertext Markup language that describes some feature of the contents of a web page. The information that you supply in a meta tag is used by the search engines to index a page. The meta tag is located next to the top of the HTML in a web page as fraction of the heading.
Meta elements are typically used to specify page description, keywords, author of the document, last modified, and other metadata.
Meta tag contain Title tag, description and keywords of your page. Its should be defined as the well manner and according your site content.