Introduction to the Drupal 7 Field API Series

Fields are the building blocks of Drupal's powerful content modeling system and the Field API allows for the development of custom field types to suite almost any data display and collection needs. When combined with the Entity API which allows for the attachment of field's to Entity bundles (commonly known as content types) Drupal becomes infinitely flexible without requiring writing any code.

There's already a pretty large ecosystem of Drupal 7 field types implemented by either Drupal core or other contrib modules, but what happens when the one you need doesn't exist? As a module developer knowing how to implement the Drupal 7 Field API and encapsulate your custom logic and functionality into a field can often times allow you to create modules that are far more reusable since they don't assume a specific information architecture.