The modules which do all the real work.
The core package provides the primary modules for defining and executing an experiment. An experiment in this context means a sequence of actions performed on various instruments, where an instrument can be a physical instrument, like a voltmeter or a cryostat, or merely the computer (for example, waiting a specified amount of time or passing multiple actions simultaneously).
Note that all modules of the core package have been deliberately (sometimes, unfortunately, at the expense of clarity) kept free of all explicit reference to the graphical interface. This decision was made to keep open the possibility of, at some point, switching to a different graphical system or even developing a command-line interface to the software.