So there are emeritus professors, full professors, associate professors, assistant professors, and postdocs.
Which of them generally has the most time for explaining things to students? Some professors pretty much tell you what you should do for the next meeting, but then leave you to figure things out on your own. Other professors are willing to explain things to you if you don't understand them (some of them more impatient than others). For the record, I've only interacted with assistant profs and postdocs.
I know that variation *between* professors in an individual category is generally much higher than variation between professors of different categories, but it's still desirable to have the most pertinent information available before choosing a professor (and standing is one of those pieces of information).