In HTML, the <br> tag is used to insert a line break. The <br> tag is an empty element, which means that it does not have a closing tag and does not contain any content.

Here is an example of how to use a break tag in an HTML document

<p>This is a paragraph.<br>
It has multiple lines.<br>
Each line is separated by a line break.</p>

The output of the break tag

This is a paragraph.
It has multiple lines.
Each line is separated by a line break.