For a Drupal site with well-designed URLs, the Path Module is essential.
Clean URLs will allow you to have http://www.example.com/node/2 instead of http://www.example.com/?q=node/2. You'll want to enable Clean URLs.
The Path Module takes this one step further, and allows you to have http://www.example.com/about instead of http://www.example.com/node/2.
Being able to control and design URLs is just one more feature of Drupal that makes it a great content management system.