<!DOCTYPE html> - it defines that the document is HTML5 (currently the newest HTML version). Every HTML file starts with this.
<html></html> - it marks the start and end of the HTML document.
<head></head> - it encloses the header of the document; here we place the title of the document, other references. The descriptions given here do not appear inside the browser window.
<body></body> - it encloses the content that will appear inside the browser window.
<title></title> - the enclosed text appears on the title bar of the browser.
<link> - it refers to an outside file.
<link rel="icon" href="the path to the icon" type="image/ico"> - it can be used to put a small picture before the text of the title on the title bar of the browser
They are used to leave comments in our code, which are not shown in the browser. Comments may help later if we want to continue the work on our webpage, to know where we left of.
<!-- write your comment here -->
<!--must continue here -->