Plugin

In computing, a plug-in is a set of software components that adds specific capabilities to a larger software application. If supported, plug-ins enable customizing the functionality of an application. For example, plug-ins are commonly used in web browsers to play video, scan for viruses, and display new file types. The image on the right is a screenshot of common Firefox web browser plug-ins. The Adobe Acrobat, QuickTime, and Microsoft Office 2007 plug-ins add the capability to display new file types inside the Firefox web browser. Add-on is often considered the general term comprising snap-ins, plug-ins, extensions, and themes.