To explain the mystic ways of academics: There are four general levels of being a professor. The least desirable is adjunct (indentured servant) in which you have no benefits, no job security and get paid a pittance ($2,000-4,000 per class). The normal starting point is assistant professor. That is full time and hence has benefits and such. The next step up is associate which is reached by achieving a certain number of years of experience plus establish credentials by publishing and such. There is also usually a raise for getting promoted. Full professor is considered the top and it reached by experience and establishing oneself as a national recognized expert-usually by various publications and completing a book. There is also a pay raise. Tenure is distinct from promotion, but people usually go for tenure when they go up for associate. It takes about 6 years to get tenure. It is achieved by showing that you have what it takes to be a good colleague and a professional. The main thing about tenure is that it is job security-you cannot be fired except for due cause (and it must be something rather bad). It was originally intended to protect academic freedom so people would not be fired for holding unpopular beliefs. Of course, since it takes about 6 years to get it, most serious rebels would not make it that far.