Fair Labor Standards Act: A federal law which establishes minimum wage, overtime pay eligibility, recordkeeping, and child labor standards affecting full-time and part-time workers in the private sector and in federal, state, and local governments.
Labor Unions: Organizations that represent workers' interests to management in businesses. They often negotiate wages, work rules, complaint procedures, rules governing hiring/firing/promotion of workers etc.
Overtime Pay: Additional pay granted to employees who have worked over their set number of hours. Typically it's calculated as time-and-a-half or double time.