I’ve always considered hotpot a crock with a lid.
Shabu shabbu is where they give you meat and veggies on a platter and you swish it around in boiling water - the name comes from the motion and sound. You compete with everyone at the table to get access to the water pot :)
Yaki niku is the same thing but you grill or fry it. You compete with everyone at the table to get better access to the grill/pan :)
Nabe is typically a big crock with a lid (typically really thick pottery or cast iron - what I think of as a hotpot). Everything in it boiling (sometimes baking) and then when they bring it to the table everyone competes to get their favorites after the lid is taken off. A lot of times they’ll keep it boiling at the table and continue to add additional things as items are consumed.
the best part of all three is taking the leftovers the next morning and adding rice and a little sugar to the mix - makes something called zou sui (spelling?). This little piece of heaven is sorta a porridge. They often will make it for people who are sick due to the high calorie content.
wow, thanks for the breakdown!