Every element of information is called node. At the base of the system is the data pool which is the collection of nodes. Next are the modules that are functional plug-ins. Modules may be drupal core or a contributed item. Blocks and menus form the next layer of drupal. Blocks are output tool. A user can configure blocks to create a display that he wants and show only a few pages. In the next layer, user permissions are determined to the type of users who would be allowed to work on the database. Template, which is the theme of the site, is the last layer. It is made of a combination of XHTML, CSS and PHP.