:: What is Mod_rewrite
Mod_rewrite provides a powerful way to do URL manipulations and made more user friendly, by configuring rewrite rules, rather than modifying the webserver software.
:: How to enable mod_rewrite on apache
+ configure httpd.conf
Just setup / configure AllowOveride on your httpd.conf or vhost configuration like:

AllowOveride All

so configure httpd.conf / vhost configuration like this:

vi httpd.conf

Add or setting vhost some like this:

   ServerName blackonsole.org
   ServerAlias www.blackonsole.org
   DocumentRoot /var/www/blackonsole
      Options Indexes FollowSymLinks
      AllowOverride All
      Order allow,deny
      Allow from all

+ restarting apache

apachectl restart

+ Google
+ WebTutorial