What Is HTML

Introduction

HTML (HyperText Markup Language) is how you describe the structure and meaning of a web page—headings, paragraphs, links, images, forms, and more. Browsers read HTML and turn it into the page users see. This chapter explains what HTML is, how it fits with CSS and JavaScript, and who this track is for—before you install tools or write your first file.

Prerequisites

None for this introduction
A modern browser (Chrome, Edge, or Firefox) helps if you peek at examples
Later chapters assume a text editor such as VS Code

What HTML Does

HTML is not a programming language. You do not write loops or business logic in HTML. You mark up content so software can interpret it:

You write	The browser understands
`<h1>Welcome</h1>`	A top-level heading
`<p>Hello, world.</p>`	A paragraph
`<a href="/docs">Docs</a>`	A link to another page

Every public website—blogs, shops, dashboards, documentation sites like hello_code—serves HTML (or HTML produced by a framework) to the browser.

Here is a tiny page you could open locally:

html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>My First Page</title>
  </head>
  <body>
    <h1>Hello, HTML</h1>
    <p>This is a paragraph on the web.</p>
  </body>
</html>

Save it as index.html, double-click it, and the browser renders the heading and paragraph. You will build pages like this step by step in later chapters.

HTML, CSS, and JavaScript

Modern front ends use three layers:

Layer	Role	Analogy
HTML	Structure and semantics	Skeleton and outline
CSS	Presentation (colors, layout, fonts)	Skin and clothing
JavaScript	Behavior (clicks, fetch, updates)	Muscles and reflexes

HTML should answer: what is on the page (title, nav, article, button). CSS answers: how it looks. JavaScript answers: what happens when the user interacts.

Tip

Learn HTML First

You can style a page badly with inline hacks, but you cannot replace HTML with CSS or JS alone. Solid HTML makes every later skill easier—including the JavaScript track on this site.

Backend developers (Java, Node, etc.) often generate HTML from templates or APIs. The markup rules are the same whether you type it by hand or a server prints it.

How the Browser Uses HTML

When you open a URL or a local .html file, the browser:

Downloads HTML (and linked CSS, JS, images)
Parses tags into a tree called the DOM (Document Object Model)
Applies CSS to build a render tree
Paints pixels on screen

You do not need to master the DOM yet. The important idea: HTML is the source document the browser parses. DevTools let you inspect that tree; you will use them in the environment chapter.

plaintext

HTML file  →  parse  →  DOM tree  →  (+ CSS)  →  visible page

JavaScript can read and change the DOM after load—that is how dynamic sites update without a full reload.

HTML5 and Living Standards

HTML5 is not a separate product you install. It is the current generation of the HTML standard: semantic elements (<nav>, <article>), native <video>, better forms, and clearer rules for parsers.

Specifications are maintained as the HTML Living Standard (WHATWG). Browsers implement what is in that document; features evolve continuously rather than in rare “HTML 6” releases.

For day-to-day work:

Use lowercase tag names (<section>, not <SECTION>)
Prefer semantic tags over piles of <div>
Validate important pages with the W3C validator (covered later in this track)

Warning

Do Not Chase Deprecated Tags

Avoid legacy presentational tags such as <font> and <center>. Use CSS for appearance. Avoid framesets; use modern layout with CSS.

Typical Use Cases

Scenario	How HTML fits
Marketing landing page	Sections, headings, CTAs, forms
Documentation / blog	Articles, code blocks, navigation
Admin UI shell	Forms, tables, semantic regions (often plus a JS framework)
Email (limited)	Table-based HTML subset—different rules, same markup idea
Server-rendered apps	Spring, Node, PHP output HTML strings or templates

HTML is also the accessibility and SEO foundation: screen readers and search engines rely on correct headings, labels, and landmarks—topics you will meet later in this track.

Who This Track Is For

Complete beginners who want to build web pages from scratch
Backend developers who know Java or SQL but never learned markup properly
JavaScript learners on hello_code who need structure before diving deep into the DOM
Anyone maintaining static sites, landing pages, or CMS templates

You do not need design skills to start. You need patience to write clear structure and to preview in a browser often.

How This Tutorial Is Organized

You will move from document skeleton → text and links → media → tables and forms → semantic layout → accessibility and SEO → small projects and deployment. Examples stay plain HTML without React or Vue so the markup stays visible.

Related hello_code paths:

Track	Connection
JavaScript	Behavior and DOM after HTML structure
CSS	Presentation layer for markup you write here
Vue	Framework templates build on HTML semantics (forms, accessibility)
Linux	Serving static files and Nginx
Java	Server-side apps that emit HTML

FAQ

Is HTML a programming language?

No. It is a markup language—a vocabulary of elements that describe document structure. Programming languages express algorithms; HTML describes content.

Do I need to memorize every tag?

No. Learn the common set (html, head, body, h1–h6, p, a, img, ul, form, input, semantic layout tags). Keep MDN HTML reference bookmarked for the rest.

Can I build a full app with only HTML?

Static sites, yes. Interactive apps need CSS and usually JavaScript. HTML remains the structural layer.

HTML vs XHTML?

XHTML was a stricter XML-based variant. Modern projects use HTML5 syntax in .html files. You rarely start new work in XHTML.

What is the difference between HTML and the DOM?

HTML is the text in your file. The DOM is the in-memory tree the browser builds from that text (and updates when scripts run). Editing HTML changes what gets parsed; scripts can change the DOM without changing the file on disk.

What comes next?

How web pages work — URLs, HTTP, and how a file becomes a page in the browser.