Pretty URLs - a guide to URL rewriting

"A lot of today's content on the web is dynamic - that is, the page you see does not physically exist on the server but instead is put together on the fly by a server-side script. Commonly, the method for passing data to the script is via the query string. The resulting links to your pages can therefore end up complicated and unfriendly. For example: http://yourdomain.com/articles/show.php?category=8&article=145&page=3

The concept of "pretty URLs" involves converting these complex dynamic URLs into easier to read, static URLs: http://yourdomain.com/articles/8/145-3.html

For the sake of clarity and to save unnecessary repetition, I will refer to the first format as "ugly" and the second as "pretty" for the rest of the article. These terms are commonly used with regards to this technique."

http://www.roscripts.com/Pretty_URLs_-_a_guide_to_URL_rewriting-168.html