Plug-in
A plugin (or plug-in) is a computer program that can, or must, interact with another program to provide a certain, usually very specific, function. Typical examples are plugins to display specific graphic formats (e.g., SVG if the browser doesn´t include this format by default), to play multimedia files, to encrypt/decrypt email (e.g., PGP), or to filter images in graphic programs. The main program (a web browser or an email program, for example) provides a way for plugins to register themselves with the program, and a protocol by which data is exchanged with plugins.
Many professional software packages offer plugin APIs to developers, in order to increase the utility of the base product. Examples of these include:
Some small software vendors produce no stand-alone software at all, but plugins for a certain product. In order to make such a position more viable as a business, open APIs are provided to allow application vendors to change their product or go out of business without destroying the cottage industries that grow up around them. Examples of such APIs include Audio Units and VST.
A pluginbrery is a plugin library used for all the web browsers in an operating system. So, instead of installing similar plugins for different browsers in the same operating system, the user can install the same plugin (in the pluginbrery) for all the Internet browsers. This can be used for functionality including:
