This is the 6508th most frequent Chinese word.
教书
Teach; to teach (as a profession).
Here, '教书' is used to mean 'teaching' in the context of a formal educational setting.
他在学校教书。
He teaches at the school.
In this sentence, '教书' expresses the activity of teaching, emphasizing the teacher's passion for the profession.
她喜欢教书，因为她喜欢帮助学生学习。
She enjoys teaching because she likes helping students learn.
'教书' is used to refer to the teaching profession as a whole in this general statement.