Flat-spectrum radio quasars are a type of active galactic nucleus that emit strong radio waves. They are characterized by their flat radio spectra, meaning their radio emissions do not vary much with frequency. This flatness indicates that the emissions come from a compact region, often associated with a supermassive black hole at the center of the galaxy. These quasars are among the most luminous objects in the universe and can outshine entire galaxies. They are important for studying cosmic evolution and the behavior of matter in extreme gravitational fields, providing insights into the nature of black holes and galaxy formation.