IFR, or Instrument Flight Rules, is a set of regulations under which a pilot operates an aircraft in weather conditions generally poor enough to require reliance on instruments for navigation and control. This system allows pilots to fly in clouds or low visibility, using instruments to guide them rather than visual references. Under IFR, pilots must file a flight plan and receive clearance from air traffic control. This ensures safe navigation and separation from other aircraft. IFR is essential for commercial aviation, allowing flights to operate safely in various weather conditions and busy airspace.