The CLIM breakdown, Arthur Lemmens style:

CLIM generalizes Lisp's textual read-eval-print loop to a read-command evaluate-command present-result loop. Commands can be read from a character-based input-stream but can also be “read” by “parsing” events. The same principle goes for presenting results: you can present a result by printing strings to a standard output-stream, but you can also present results in a graphical way.