Software that adds functionality to a Web browser. Typically from a third party rather than the browser developer and also called "add-ons" or "extensions," they are used to add toolbars and support a variety of graphics, animation, audio and video formats. For example, the Flash plug-in lets users watch countless videos on the Web in the Flash video format. The terms "browser plug-in" and "helper application" are sometimes used synonymously; however, the plug-in is designed for and entirely integrated into the browser and cannot run by itself. A helper application is a separate program launched by the browser when needed. See helper application, plug-in, extension and plug-in free.