Plugins and filters

A plugin (plug-in, addin, add-in, addon or add-on) is a computer program that interacts with a host application (Photoshop, in this case) to provide a certain, usually very specific, function on demand. Plugins are extensions to the host software that modify or add to existing functionality. Some basic plugins generally rely on the main application's user interface and have a well-defined boundary to their possible set of actions. Other more advanced plugins have fewer restrictions on their actions, and may provide their own user interfaces. There are enough Photoshop plugins available to achieve almost any effect imaginable. There are even some plugins that can be used to create other plugins without the need of complex programming, or no programming knowledge at all.