Semantic HTML introduce the meanings of a web page instead of the only presentation. A simple way to understand is
Semantic elements = elements with a meaning.

Examples of non-semantic elements: <div> and <span> – Defines nothing about its content.
Examples of semantic elements: <form>, <table>, and <article>- Clearly defines the purpose of its content.

HTML5 offers a lot of semantic HTML elements and all the modern browsers support those. Some of the semantic elements are

    

<article>    

<aside>    

<details>

<figcaption>    

<figure>    

<footer>    

<header>
<main>
<mark>    

<nav>    

<section>    

<summary>
<time>