For WME to recognize a DLL library as a plugin:
This function returns some basic information about the plugin, its description, version and the engine version this plugin is designed for.
This function returns a list of script classes provided by this plugin. It can be one name or a comma separated list of names if the plugin provides several classes.
This function returns an interface for each of the provided script classes. It returns a set of function pointers for each of the classes. These functions define the behavior of the class and include e.g. a constructor, a destructor, an event receiver etc. More on that later.