The meta tag should still be defined in HTML 5 like XHTML.
it’s generally used to describe a characteristic of a Web page, such as the character encoding. Character encoding is the internal representation of letters, numbers, and symbols in a file such as a Web page or other file that is stored on a computer and may be transmitted over the Internet. There are many different character encoding sets. However, it is common practice to use a character encoding set that is widely supported, such as utf-8, which is a form of Unicode. The below meta tag indicates
that the content of the document is a Web page that uses utf-8 character encoding.
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
although your page will continue to work without defining this tag, it better to define it to get a green ribbon on Validator!