Root & metadata
<!DOCTYPE html> HTML5 document type
<html> Root of the whole page
<head> Settings & metadata
<title> Browser tab title
<meta> SEO & character data
<link> Link to an external file (CSS)
<style> Internal CSS code
<script> JavaScript code
Semantic structure
<body> Visible content
<header> Header or top bar
<nav> Navigation menu links
<main> The page's main content
<section> Thematic sections
<article> Independent article or post
<aside> Side content (sidebar)
<footer> Site footer
<div> Meaningless box (grouping)
<span> Inline meaningless box
Text & Formatting
<h1> to <h6> Headings (H1 is the most important)
<p> Paragraph
<br> Go to the next line
<hr> Horizontal separator line
<strong> / <b> Bold (with/without meaning)
<em> / <i> Italic and emphasized
<mark> Yellow highlight
<del> / <ins> Deleted / inserted
<sup> / <sub> Superscript / subscript
<blockquote> Long quotation
Lists
<ul> Unordered list (bulleted)
<ol> Ordered list (numbered)
<li> Item inside a list
<dl> Definition list
<dt> Term being defined
<dd> Definition text
Links & media
<a href=""> Link or anchor
<img src=""> Image (no closing tag)
<audio controls> Audio player
<video controls> Video player
<source> Media file source
<iframe src=""> Frame showing another site
<figure> Image + caption container
<figcaption> Image caption
<canvas> Drawing canvas with JavaScript
<svg> Vector graphics
Tables
<table> Main table container
<caption> Table title
<thead> Table header
<tbody> Main table body
<tfoot> Table footer
<tr> A row
<th> Header cell (bold)
<td> Regular data cell
Forms
<form> Data container
<input type=""> Input field
<textarea> Multi-line text input
<button> Click button
<label for=""> Field label
<select> Selectable dropdown list
<option> Dropdown list options
<fieldset> Group related fields
<legend> Fieldset legend
Interactive & important features
<details> Accordion (collapsible)
<summary> Accordion summary
<dialog> Modal / Popup window
class="" Class styling attribute
id="" Unique ID attribute
data-*="" Custom hidden data attribute
hidden Completely hide element
contenteditable Make tag editable