Rewriting URL's with .htaccess

Rewriting product.php?id=12 to product-12.html

It is a simple redirection in which .php extension is hidden from the browser’s address bar and dynamic url (containing “?” character) is converted into a static URL.

RewriteEngine on
RewriteRule ^product-([0-9]+)\.html$ product.php?id=$1

For more reference on this refer:
http://roshanbh.com.np/2008/03/url-rewriting-examples-htaccess.html