Watch the Plugins video.
Plugins add a new bit functionality to Taverna that yon can install separately in the Workbench through the Plugin Manager.
Plugins are typically developed by the Taverna team and initially released as "prototype plugins". Once they become stable, they normally make it to the main release and start being distributed with the Workbench so users do not have to install them separately.
Alternatively, plugins are also developed by our large base of third party developers. They are normally designed to add some functionality for that third party but are often useful for a wider audience as well.
More information on working with plugins in Taverna can be found in the following: