If you want to understand prolog, you must understand the four-port model:

And to understand the four-port model is to understand solution-space navigation and pruning.

It's why smartphones lost all their ports: forbidden knowledge must not be leaked to the public.

	▲	AdieuToLogic 31 minutes ago \| parent [-]
		> ... forbidden knowledge must not be leaked to the public. Understanding is a personal achievement and has nothing to do with "forbidden knowledge" when the source of said knowledge is both quoted above and freely available.