To insert a line break in your HTML document, you can utilize the <br> tag.

<br> tag is used to insert line breaks in text or paragraphs.

The syntax for the <br> tag looks like this:

<br>

The <br> tag is commonly referred to as an empty or self-closing tag, meaning it doesn't require a closing tag. This tag is responsible for breaking text lines or separating paragraphs. When implemented, it automatically moves the text following the tag to the next line.

It's particularly useful in formatting textual content where line breaks are essential for readability or visual layout. For instance, it can be used in addresses, poems, or song lyrics to preserve the original line structure.

Here is a quick video showing how to use the <br> tag: