The Auger Engineering Radio Array (AERA) located at the Pierre Auger Observatory in Mendoza, Argentina, measures the radio emission of extensive air-showers initiated by cosmic rays with energies above 0.1 EeV. More than 150 autonomous antenna stations, spread over 17 km² measure radio signals in the frequency range of 30 – 80 MHz. The operation of AERA within the Pierre Auger Observatory offers a unique opportunity to cross-calibrate the radio measurements with the water-Cherenkov detector and the fluorescence detector. With AERA a precise measurement of the energy of cosmic rays has been achieved including a detailed analysis of the systematic uncertainties. The optimized reconstruction of the maximum shower depth can be validated using the longitudinal profile coincidently measured by the fluorescence detector. Enlarged footprints have been detected for horizontal air showers with signals at the surface up to 15 km from the shower core. This contribution gives an overview of the AERA detector with the different stages and station- types, as well as of the AERA results.