Drupal 7 introduced many new APIs, most notably the Field API. The Field API is a powerful but complex system that defines the structure and behavior of fields. It introduces several new concepts including bundles, field storage, field types, widgets, and formatters. Fields describe the data structure and behavior, while instances store widget and formatter settings and are easier to update. The Field API provides functions to attach, load, and update fields on entities. It handles fields already attached rather than the attachment process itself. Taxonomy terms are also now full entities with their own API.

1. Drupal 7: What's new Karoly Negyesi Clarity Digital (examiner.com)

2. What's new in Drupal 7 See http://blip.tv/file/2772239

3. Tons of new APIs

4. Most of them are well documented and easy

5. Field API: many new concepts and gotchas

6. Field API Extremely powerful

7. API and not browser driven

8. Our work now is “precision surgery”

9. Key concepts Bundles

10. Field storage

11. Field types

12. Widgets

13. Formatters

14. Fields

15. Attach

16. Instances

17. Anatomy of a node Organization: node type

18. Primary identifier: nid

19. Version identifier: vid

20. Anatomy of a term Organization: vocabulary