<meta>

//define the character set used
<meta charset="UTF-8">

//define a description of your web page
<meta name="description" content="Free Web tutorials">

//define keywords for search engines
<meta name="keywords" content="HTML, CSS, XML, JavaScript">

//define the author of a page
<meta name="author" content="John Doe">

//refresh document every 30 seconds
<meta http-equiv="refresh" content="30">

Is used to specify which character set is used, page description, keywords, author, and other metadata.

//you should include the following <meta> viewport element in all your web pages
<meta name="viewport" content="width=device-width, initial-scale=1.0">

• HTML5 introduced a method to let web designers take control over the viewport, through the <meta> tag.
• A <meta> viewport element gives the browser instructions on how to control the page's dimensions and scaling.
• The viewport is the user's visible area of a web page, it varies with the device, and will be smaller on a mobile phone than on a computer screen.