Within the code these drop-in shared object files are called modules. In the user interface they are called plugins. Modules seems to be clearer to developers while plugins clearer to end users. Additionally, all modules MUST be subclasses of the plugin object. The first five, which return char pointers, are used to identify the module to the client and to the user.
Group returns a the group it belongs to, e.g. servers.
Look at what groups names are currently in use by other plugins to see if yours fits in to any of them. If not, you can define a new group. The client takes care of arranging the groups, all you need to do is provide a name. This is for the users, so it should be brief, clear and not too technical. Do whatever you need to do upon getting focus.