PLUGIN (Mac OS X Plug-in)
The PLUGIN Misc file format
Files with the PLUGIN extension are generally used for many plugin files. The most well-known, however, is associated with the Mac OS X operating system. PLUGIN files are used on Mac computers to add additional and new applications, features and plugins to programs installed on the Mac.
Technical details of PLUGIN files
PLUGIN files are often part of the installation of a Mac OS X software program or application. In these cases, the PLUGIN files are stored together with the other installation files of the application. Independent or additional plugins can be installed in the corresponding folders of the program's library folder.