The hot water is recirculated during the wash, the rinse uses fresh water from the tap with the excess going out an overflow. A little sump water gets replaced every cycle, but enough stays that it's back up to temperature before you've emptied and refilled it. There's also a small peristaltic pump to top up the detergent directly from the bottle.
Not much benefit in a home setting unless you fancy having it hot and ready 24/7 though.
This is probably the one trick consumer dishwashers should emulate
the task is prepare food, eat, clean. when you leave the kitchen and come back the next day the task is now different, its unpack, prepare,eat,clean.
you are constantly not finishing today's tasks. it lives to see another day. if you can fix it, bound it to the workflow, you will be a billionaire