What is a superheterodyne receiver and why is it commonly used?

A superheterodyne receiver converts the incoming RF signal to a fixed intermediate frequency (IF) before demodulation. It consists of: RF amplifier, local oscillator, mixer (produces IF = RF - LO), IF amplifier and filter, and demodulator. Advantages: Selectivity and gain at fixed IF are easier to optimize, tuning requires only changing LO frequency, and image rejection can be implemented. It is the dominant receiver architecture for radio, TV, and wireless communications due to its flexibility and performance.