A lightweight framework makes up the Drupal core. This is what you get when you download Drupal. The core is responsible for providing the basic functionality that will be used to support other parts of the system.
The core includes code that allows the Drupal system to bootstrap when it receives a request, a library of common functions frequently used with Drupal, and modules that provide basic functionality like user management, taxonomy, and templating, as shown in Figure 1-2.
The administrative interface in Drupal is tightly integrated with the rest of the site and, by default, uses the same theme. The first user, user 1, is the superuser with complete access to the site. After logging in as user 1, you'll see an Administer link within your user block. Click that, and you're inside the Drupal administrative interface. Each user's block will contain different links depending on their access levels for the site.