A Butterworth filter is an electronic filter designed to have a flat frequency response in the passband, meaning it allows signals to pass through without distortion. It is widely used in signal processing applications due to its smooth response and effectiveness in removing unwanted frequencies. The filter can be implemented in various forms, including analog and digital circuits. The Butterworth filter is characterized by its order, which determines the steepness of the filter's roll-off. Higher-order filters provide a sharper transition between the passband and stopband, making them more effective at filtering out unwanted signals. This makes them suitable for applications in audio processing, telecommunications, and control systems.