Summary
<!-- This element creates a line break -->
<br>
<!-- This element creates a horizontal line to divide content -->
<hr>Details
HTML code is made up of elements. Some elements are made up of a single self-closing tag, as you can see in the examples above.
A self-closing tag is made of an element’s symbol wrapped in angle brackets. It does not require a forward slash.
Elements that use self-closing tags are referred to as empty elements.
Demo
References
HTML basics on MDN