Plug-in files are used to add additional functionality or to enhance existing features of software applications. Many editing type applications use plug-in files, an image editing application may use a plug-in file to add support for exporting to a new image format or to add a new effect to an image whereas a media player may use a plug-in file to allow the play-back of a previously unsupported media format.
Other types of software that may use plug-in files include web browsers, office applications and even computer games.
