why html tags work in xml?

["Kumar, Ritesh (GEP, Contractor)" <Ri...@gepex.ge.com>]

Hi 
     Why is that when you give an opening and closing tags for some tags in
html, they work fine in xml ! even though there are not closing tags for
them ( tags ) in html.For example:

There  is no closing tag for <br> in html, but when you give
 <br> some text</br>
 <br> some text</br>
it works fine in xml, atleast the desired output is displayed.
Simillar is the case with <Img> tag and <hr> !!! 

What is the correct way of  using these tags / corresponding tags in xml ?


Thanks
Ritesh Kumar