When an area that support plug-ins executes in EPiServer it will search for files in the bin directory and their containing classes for an attribute called PlugInAttribute. The PlugInAttribute is only a base class for all specialized plug-in types and is not actually used anywhere to define a plug-in, only to search and match plug-ins that used attributes derived from PlugInAttribute.

The class that handles searching is PlugInLocator, probably you don’t need to use this class unless you are implementing your own plug-in support. It returns a array of PlugInDescriptor classes, PlugInDescriptor contains information about the PlugInAttribute definition and the plug-in id that was assigned to the plug-in in this installation.