A periodic flight review is mandated for pilots by the aviation authorities of many countries. The review takes different forms in different countries.
For holders of pilot certificates issued by the United States Federal Aviation Administration a flight review (previously the FAA referred to this as a biennial flight review, usually abbreviated BFR) is a review required of every active holder of a U.S. pilot certificate at least every 24 calendar months. The flight review consists of at least 1 hour of ground instruction and 1 hour in-flight with a qualified flight instructor.
Before being able to act as pilot in command (PIC) a pilot must have completed a flight review within the previous 24 calendar months. The FAA and instructors are quick to point out that it is not a test. There is no pass or fail criteria, although the instructor giving it can decline to endorse your log-book that a flight review has been completed.
A flight test (administered by an FAA representative or Designated Pilot Examiner) that leads to a new certificate or rating may be substituted for the flight review. Completion of a proficiency check administered by a check airman (typically air carrier pilots) can also be used.