well, for one, you can learn more about it here:
http://www.webune.com/forums/learn-how-to-use-apache-module-mod-rewrite-explained-t281.html
mod_rewrite is search engines's best friend to your site. Specifically if you are dynamic web sites with the popular PHP programming language.
The mod_rewrite module uses a rule-based rewriting engine that is based on a regular-expression parser to rewrite requested URLs on a real time basis. It supports an unlimited number of rules and an unlimited number of attached rule conditions for each rule to provide a really flexible and powerful URL manipulation mechanism. The URL manipulations can depend on various tests, for instance server variables, environment variables, HTTP headers, time stamps and even external database lookups in various formats can be used to achieve a really granular URL matching.
This module operates on the full URLs (including the path-info part) both in per-server context (httpd.conf) and per-directory context (.htaccess) and can even generate query-string parts on result. The rewritten result can lead to internal sub-processing, external request redirection or even to an internal proxy throughput.
But all this functionality and flexibility has its drawback: complexity. So don't expect to understand this entire module in just one day.
This module was invented and originally written in April 1996
and gifted exclusively to the The Apache Group in July 1997 by
Ralf S. Engelschall
rse@engelschall.com
www.engelschall.com