vBulletin Supports API Extensions which allow Addon Developers to create extensions to the core of the software itself. These aren't plugins but extensions of the actual classes of plugins. Installed predominantly in a central location, auto-installing and more capable than plugins. Extensions tie directly into the existing API classes and extend them. They can provide output via template hooks, insert template hooks into templates and include their own templates, etc... Templates themselves are more robust as well as they can pull information directly from the database using special tags, if needed and without additional coding.