University professors are divided into seven grades. University professors are classified into distinguished professor, first-class professors, second-class professors, third-class professors, fourth-class professors, fifth-class professors and sixth-class associate professors. Distinguished professor, as the highest level, is usually awarded to scholars who have made outstanding achievements and contributions in teaching and scientific research, followed by first-class professors, who are experts with high scientific level and remarkable achievements and contributions in teaching and scientific research. Professor level 4 is the lowest level in the title of full professor, and grades 5 and 6 are associate professors. Each level corresponds to different salary and academic requirements. Professors' job is to teach courses in the fields they are good at, or to give students professional training, such as science and literature.