In the html document, the horizontal tag element represents a horizontal line that is used to visually separate the content. It is an empty element which also means it does not have any content and there is no requirement for any closing tag.

Here is an example of how to use the horizontal tag in an html document

<p>This is some text.</p>
<hr>
<p>This is some more text, separated from the previous paragraph by a horizontal line.</p>