Both of these words refer to people who work at a company - but staff is always singular and uncountable - it describes the entire group of workers as one thing. Employees is plural and countable - it describes the collection of individual workers.
The entire staff was happy about the extra day off.
All the employees were happy about the extra day off.
Note that "staff" takes the singular verb was, and "employees" takes the plural verb were.
Whenever you use a specific number, use employees or staff members:
Back when Quicksilver started Roxy it was trying to break into what it saw as the untapped market for female surfers. It was a gutsy move but it worked out and you can see how the heart shaped Roxy logo is derived from two back to back Quicksilver logos.