The functionality that we have used so far is included in the default installation of Drupal and you don't need to do anything special to use it. However, the real power of Drupal is unleashed when you begin enabling the optional modules that are included with Drupal, and when you install contributed and custom modules.
The Drupal installation includes over 20 modules, some of which are not enabled by default. These modules may be disabled by default for several reasons. Some are disabled because they are not needed by every Drupal installation, or they may require extra configuration, or they may have an impact on performance. There are also several optional modules that are enabled by default because they are used by a majority of sites. However, if your site doesn't need the functionality they provide, you can disable them.
You can view a complete list of modules that are available on your site by clicking on the Modules link in the...