Pro Drupal 7 Development, Third Edition

Chapter 2. Writing a Module

Modules are the basic building blocks that form the foundation of Drupal and are the mechanisms for extending the functionality provided by the off-the-shelf version of Drupal, also known as Drupal core. I often explain to those who are unfamiliar with Drupal that modules are like Lego building blocks. They fit together perfectly by following a predefined set of guidelines, and with a combination of modules, you can build rich and complex solutions.

There are two general categories of Drupal modules—core and contributed. Core modules are those that are shipped with Drupal and include modules such as polls, menus, taxonomy, search, feed aggregator, and forums. Contributed modules are all of the modules created by the ...