In the new XHTML standard all tags shall also have an ending tag, or it must include a / to indicate that it's a 'loner'.
Check http://en.wikipedia.org/wiki/XHTML

>Hi, I am translating an HTML document, and was curious about an HTML code I saw repeatedly:
>
>< br / >
>
>without the extra spaces at the beginning and the end, but with a space between "br" and "/".
>
>My HTML knowledge is somewhat basic; I know about begin and end tags, but what does the slash at the end of a tag do?