The AMRAAM missile was designed to replace the Sparrow missile. AMRAAM is the AIM-120 Advanced Medium-Range Air-to-Air Missile, while Sparrow refers primarily to the AIM-7 semi-active radar-guided missile family.
The U.S. Air Force and Navy developed AMRAAM during the 1970s and 1980s to provide a more capable beyond-visual-range weapon. Unlike the AIM-7, which generally required the launching aircraft to keep illuminating the target with radar, AMRAAM uses inertial guidance during much of its flight and activates its own onboard radar near the target. This gave the launching aircraft greater freedom to maneuver or engage more than one target.
AMRAAM entered operational service in the early 1990s and became the principal U.S. medium-range air-to-air missile. The answer is sometimes confused with Sidewinder, but Sidewinder is a short-range, infrared-guided missile; AMRAAM was intended as Sparrow's medium-range successor.