these are what are called endowed professorships awarded to big name professors. a google search is all you need to know more. you are right - they are very well respected and working for them is a full time nightmare.
assistant prof -- new professors have six years to make tenure. requires publications in leading journals, good teaching evaluations and service.
associate prof-- after you make tenure.. big bump in salary. job for life unless you are really slacking off or do something immoral or illegal.
full professor -- another 4-6 year clock. big bump in salary. lot of power. lot of recognition.