It is the gold standard for professors, the ultimate guarantor of future employment. A professor who earns tenure at the University of Washington receives a nine-percent salary raise and is employed for life, barring any criminal activity or gross violations of university code. A tenured professor does not have to make his students fill out those monotonous evaluation sheets each quarter and does not have to worry about losing her position due to budget cutbacks or much of anything else. The UW is a tenure-track school, meaning that for most departments, every new teacher hired is guaranteed consideration for tenure after six years.
Many schools make no such promises.
The road to tenure is a long and often arduous one, however. During spring quarter of the second year, professors' contracts are considered for renewal. If renewed, profs are appointed to a second three-year term. They come up for tenure during their fifth year at the university. Candidates prepare portfolios of their work to present to their departments.