A link in which the URL is given in reference to the current page or to the root of the current site.
If the URL in a link begins with a file or directory name, the link is relative to the current page:
<a href="directory/file.html">link relative to current page</a>
If the URL in a link begins with a slash, the link is relative to the root directory of the current site:
<a href="/directory/file.html">link relative to root of current site</a>