<!DOCTYPE html> : indicate the filetype is html
<html>：starts of html content
<head>：html head part
<title>：tilte of the html page in browser
<body>：html body part
<p>：paragragh
<h1>：heading
<h1>,<h2>,<h3>,<h4>,<h5>,<h6>：Headings just different in size
<img src="location of the image">：add image to website
<a href="URL">：hyperlink site when click the image
詳細內容見codecademy: HTML Basic
（完）