Emacs is a LISP coding environment, and a damn good one because huge portions of Emacs are written in LISP. Well, ok, elisp, but close enough.

On the Gimp thing, Gimp macros can also be written in Python as well. He might get a kick out of writing macros in both Scheme and Python and comparing the difference. I've written Python Gimp macros, incidentally: I have one that will take a selection in an image and turn it into a black image mask, trimmed for size and ready for use to colorize a map based on data (similar to a heatmap but with discrete boundaries).

I'm glad he's so interested in how things work as opposed to just wanting to get through it. That's commendable.