plugin or plug-in

A software program that extends the capabilities of your browser in a specific way, giving you, for example, the ability to play audio samples or view movies on your computer screen.

Think of a plugin as a smaller, add-on computer program that works in conjunction with a larger application by enhancing its capabilities. Web browsers have many plugins that allow you to do a variety of things online, from viewing 3-D animation to visiting VRML worlds to hearing audio.

The difference between a plugin and Java or JavaScript is that the latter two are languages that run instantly on your browser.

A few browser plugins include: Shockwave and Flash (for animation); Acrobat (as a utility); and RealPlayer and QuickTime (for audio/video).