It has both includes (We call plugins to prevent confusion with standard includes), and Themes, which is a way of using dreamweaver templates dynamically. It also has the show if utility.
By combining plugins and themes it gives you a full framework with modular functionality and dynamic skins.
The advantage of plugins over ADDT includes are:
1) Streamlined code
2) Dreamweaver translation (so you see the contents in design view)
3) Advanced bindings for access to more parts of the page
4) Integration with dreamweaver templates (you can break your themes into editable regions and place them individually)
5) The entire Theme concept, which is unique to Framwork builder and rounds out the ability to truly skin and modularize a web page into building blocks.
6) CS5 support
7) Available to buy now (ADDT is not any more)