As illustrated in Figure., <HTML> is a starting tag. To delimit the text inside, add closing tag by a "/" to the starting tag. Most but not all tags contains a closing tag. It is essential to write the code for an HTML page among <HTML> & </HTML>. Think of tags as talking to the browser or, better still, giving it instructions. What you have just told browser is It is the start of an HTML document' (<HTML>) and "it is the end of an HTML document' (</HTML>). Now you have to put some matter in between these two markers.
Every HTML document is segregated in a HEAD & BODY. The information regarding the document is kept in <HEAD> tag. The BODY contains the page content.