Instrument Flight Rules (IFR) are regulations under which a pilot operates an aircraft in weather conditions that require reliance on instruments for navigation and control. IFR is essential when visibility is low, such as in clouds or heavy rain, ensuring safe flight by using cockpit instruments rather than visual references. Pilots flying under IFR must have specific training and certification, as well as an aircraft equipped with the necessary instruments. Air traffic control plays a crucial role in guiding IFR flights, providing instructions and clearances to maintain safe distances between aircraft in busy airspace.