Basically, there are 5 main layers in Drupal where information flows,
- Data (Node, ETC)
- Blocks and Menus
- User Permissions
Base of the system is collection of Nodes. – the data pool
These are functional plugins that are either part of the Drupal core (they ship with Drupal) or they are contributed items that have been created by members of the Drupal community.
Blocks and Menus
This is the next layer where we find blocks and menus. Blocks often provide the output from a module or can be created to display whatever you want, and then can be placed in various spots in your template (theme) layout. Blocks can be configured to output in various ways, as well as only showing on certain defined pages, or only for certain defined users.
Here is the next layer where settings are configured to determine what different kinds of users are allow to work and see.
This is mainly the site theme or the skin. This is made up predominantly of XHTML and CSS, with some PHP variables intermixed
Understanding this flow of information is very important if you are facing A Drupal project targeted interview as the interviewer might test your overall knowledgeÂ ofÂ Drupal CMS by asking this sort of questions.