Classes

Each plugin implements a class (rarely a set of classes). Classes are:
name description
(feature) random features directly accessible for the user, usually actions
(lib) support code library for other plugins (core doesn't depend on these); functionality not directly accessible for the user but other plugins may depend on it
hid Human Interface Device: interactive user interface, usually GUI
import load alien formats into the design space
export save (parts of) the design space in alien formats
fp footprint (element) library implementation
io native file format (save & load) implementation