I've always thought of it in terms of raw power.
Broilers are the high power big floor to ceiling models designed to cook a lot of protien at high temp.
Salamanders, not the amphibians, are mid range units mounted above the stove. I usually use it for gratining(How the heck do spell you spell that?) stuff and sometimes to cook fish.
On the low end you have cheese melters, which do exactly that.