What this osc contribution does is rewrites the standard dynamic URLs to more SE friendly and keyword rich URLs

in short it would turn a url from this:
www.domain.com/product_info.php?cPath=1&products_id=1
to something more descriptive like this:
www.domain.com/article-directory-turnkey-script-p-1.html

You can can clearly see how the second URL would be more descriptive and better picked up by search engines.

The installation is quite straight forward and well documented by Bobby AKA Chemo, but If you need help installing the contribution you can contact the store owner of this oscommerce hosting site. I highly recommend his work.