Plugins are small programs or applications that add additional features to an existing program. Adobe's Lightroom has supported plugins for some time now. They are a useful way to expand the functionality of the existing program without the need for using additional standalone applications. Plugins are designed to cover the gaps in features that were not originally included, or to add special effects. Often Lightroom plugins require you to export your images to a 3rd party program, but most, if not all, will return you to Lightroom when the editing is done.