So who runs it?

The head of the Department is called the Chair (man or woman). The chair has a PhD. So go ahead and call her Doctor, she’ll like that. Among other things the Chair hires the instructors who teach in the department. The main instructors the Chair hires are Professors. A professor is someone whom the chair has deemed fully qualified to teach or “profess” a subject. Rather than a job a professor receives an appointment. Within a department the Chair may have appointed several professors. A professor is often the head of a particular program within that same department. Professors nearly always have a PhD but this is not always necessarily true. In fact, you may be surprised to learn, a professor need not necessarily even have any college degree at all. She or he simply needs to have been determined to be qualified by the Chair to teach the subject. If a professor lasts long enough in a department he may be granted tenure. Depending on the school this can mean this professor cannot be fired. This can explain why, at times, some professors behave in a peculiar fashion. How would you act at work if you couldn't be fired?