The  tag defines metadata about an HTML document. Metadata is data (information) about data.

 tags always go inside the  element, and are typically used to specify character set, page description, keywords, author of the document, and viewport settings.

Metadata will not be displayed on the page, but is machine parsable.

Metadata is used by browsers (how to display content or reload page), search engines (keywords), and other web services.

There is a method to let web designers take control over the viewport (the user's visible area of a web page), through the  tag (See "Setting The Viewport" example below).