Plugins are independent programs, which are loaded into Graphics programs, to amplify or add capabilities to the program.
There are many Plugins available, not only as commercial products but shareware and freeware, which have a variety of functions.
Kai's Power Tools or other wise known as KPT is an exceptional collection of image filters that produce unlimited effects for print and the Web. Includes 10 plugins that extend and enhance the creative possibilities of Paint Shop Pro and compatible products.
KPT requires a host application to run. The host application can be any program that supports Adobe Photoshop compatible plugins.