Tagname: <HTML>
Purpose: Declares the document to be an HTML document. All document
content and supporting HTML code goes between the <HTML> and </HTML> tags.
Usage: <HTML> ... </HTML>
Example 1: Normal HTML
<HTML>
... all content and HTML code goes here ...
</HTML>
Example 2: Because standards have been introduced for HTML, the same
can include DOCTYPE
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<HTML>
... all content and HTML code goes here ...
</HTML>
Technically, <!DOCTYPE> is an SGML tag, not an HTML tag, so it is acceptable for it to be outside the <HTML> and </HTML> tags.
Tagname: <HEAD>
Purpose: Contains the tags that compose the document head.
Usage: <HEAD> ... </HEAD>
Example:
<HTML>
<HEAD>
... tags making up the document head go here ...
</HEAD>
... all other content and HTML code goes here ...
</HTML>