staff member vs employee

staff member and employee both are nouns.

Word	Noun	Adjective	Verb	Adverb
staff member	Yes	No	No	No
employee	Yes	No	No	No

As nouns, employee is a hypernym of staff member; that is, employee is a word with a broader meaning than staff member:

staff member: an employee who is a member of a staff of workers (especially a member of the staff that works for the President of the United States)
employee: a worker who is hired to perform a job

staff member (noun)	employee (noun)
an employee who is a member of a staff of workers (especially a member of the staff that works for the President of the United States)	a worker who is hired to perform a job