.PLUGIN File Extension

Adds additional features or hardware support to programs in Mac OS X; often installed in a folder within the main Library folder; common examples include the "/Library/Internet Plug-Ins" and "Library/Printers/[Manufacturer]" folders.

Plugin files may also be installed with various Mac OS X applications. These plugins are typically stored within the corresponding application folder.

Plugin used by Photoshop, an image-editing application; stores content that extends the functionality of the default Photoshop application; often used for adding image effects and filters, or support for a new raster image format.

Several preinstalled PLUGIN files are stored in Photoshop installations within the Plug-ins directory.

NOTE: Plugins may be created and sold by third-party developers.