The Uniform Resource Locator (URL)
A URL, or address, is a path through directories from the site’s root to a particular file. There are two types of URLs, relative and absolute.
Absolute Addresses
An absolute address is the url. The following link uses an absolute address mapped to example.com:
<a href="http://example.com">
Example.com</a>
Relative Addresses
A relative address bases your next move on its current position in the file structure on the server.
If you were at http://example.com/page2.html, and you wanted to make a link to page3.html, you would simply type:
<a href="page3.html">
Page 3</a>
Besides being less to type, it has a great advantage over the absolute address. If you were to move example.com to examplemania.com, you will need to rewrite every absolute address, but the relative address stay the same.