Some html tags neither have content nor do they have an end tag they are called empty tags.
An empty element can not have nested elements. No child nodes.
Following is the list of empty tags. (in HTML putting an end tag to an empty tag is invalid. )
<area>
<base>
<br>
<col>
<embed>
<hr>
<img>
<input>
<keygen>
(HTML 5.2 Draft removed)<link>
<meta>
<param>
<source>
<track>
<wbr>
Reference :https://developer.mozilla.org/en-US/docs/Glossary/Empty_element