Tags for Empty Elements
[44] EmptyElemTag ::= '<' Name (S Attribute)* S? '/>' [WFC: Unique Att Spec]

Empty-element tags may be used for any element which has no content, whether or not it is declared using the keyword EMPTY. For interoperability, the empty-element tag SHOULD be used, and SHOULD only be used, for elements which are declared EMPTY.

Examples of empty elements:

<IMG align="left"
src="http://www.w3.org/Icons/WWW/w3c_home" />
<br></br>
<br/>