Empty Elements
Some elements shouldn't have content inside them, for example breaks or images, since it's hard to see how that would make sense. Another example is the link element.
All empty elements have only one tag and before the closing '>' you need a space, followed by a '/'.
break is <br />
image is <img src="images/me.jpg" alt="picture of myself" />
In HTML5 these are called void elements and have a few differences(follow the void link)