As the name implies, commercial pilots can be paid to fly aircraft.
Commercial pilots must be at least 18 years old and have a minimum of 250 hours of flight time (190 hours under the accelerated curriculum defined in Part 141 of the federal aviation regulations), including 100 hours in powered aircraft, 50 hours in airplanes, and 100 hours as pilot in command (of which 50 hours must be cross-country flight time). They must hold an instrument rating, or be restricted to flying for hire only in daylight, under visual flight rules (VFR), within 50 miles of the originating airport. They may fly for hire in accordance with applicable parts of the federal aviation regulations.
Commercial pilots must have a current and more stringent Class II medical, which they must renew every 12 months. They must revalidate their pilot certificates every 24 months by undertaking a flight review with a certified flight instructor (CFI).