What are plugins?

Some articles on plugins, plugin:

Cotonti - Features
... user registration additional features can be added to the default engine via plugins ... Cotonti has support for Seditio plugins as well as a growing library of its own plugins ... Support for multilingual sites allows for templates and plugins to be customized to support a wide variety of users on a single site ...
List Of Dock Applications
... Customizable dock with support for plugins and skins ... Support for docklets (plugins) ... Support for docklets (plugins) ...
Carrier (software) - Features - Plugins
... Various other features are supported using third-party plugins ... Such features include Encryption and privacy, through Off-the-Record Messaging (OTR) Notifications (such as showing "toaster" popups or Snarl notifications, or lighting LEDs on laptops) Showing contacts what you are listening to in various media players Adding mathematical formulas written in LaTeX to conversations Watching videos directly into your conversation when receiving a video sharing website link (YouTube, Vimeo) ...
Google Chrome - Features - Security - Plugins
... Chrome supports plug-ins with the Netscape Plugin Application Programming Interface (NPAPI), so that plug-ins (for example Adobe Flash Player) run as an unrestricted ... NPAPI that is more portable and more secure called Pepper Plugin API (PPAPI) ...
SOBI2 - Features - Plugin Interface
... Sobi2 plugins enhance the functionality of Sobi2 ... There are plugins available to add an image or media gallery or to use Sobi2as a download directory ... Some of the plugins to Sobi2 include a Review Rating Plugin and Gallery Plugin ...