These employees are classified as nonexempt because they aren't exempt from the Fair Standards Labor Act. In all states, this means your employee is entitled to overtime pay at 1 1/2 times their hourly wage if they work over 40 hours a week. Additional rules apply in certain states, and generally speaking these employees are entitled to a break after a certain number of hours working.
If you hire non-exempt employees, be certain to carefully calculate their overtime pay to avoid running into legal difficulties. You'll also need to keep in mind that it's usually illegal to compensate for overtime with comp time instead of additional pay.