HTML <hr> tag is used to specify a paragraph-level thematic break in HTML document. It is used when you abruptly change your topic in your HTML document. It draw a horizontal line between them. It is also called a Horizontal Rule in HTML.

---

HTML hr tag

<h2>HTML</h2>  
<p>HTML is a language for describing web pages.</p>  
<hr/>  
<h2>HR Tag </h2>  
<p> HR tag is used to draw a horizontal line within the texts to sepate content.<p>  

Output:

HTML

HTML is a language for describing web pages.

---

HR Tag

HR tag is used to draw a horizontal line within the texts to separate content.

---

HR tag in HTML 4.01 and HTML5?

In HTML 4.01, the <hr> tag represents a horizontal rule while in HTML 5, it defines a thematic break. CSS is used in HTML5 instead of layout attributes.

---

HR tag in HTML and XHTML

In HTML <hr> tag need not to be closed whereas <hr> tag must be properly closed in XHTML.