A bandpass filter is an electronic device that allows signals within a specific frequency range to pass through while blocking signals outside that range. It is commonly used in various applications, such as audio processing and telecommunications, to isolate desired frequencies from unwanted noise or interference. These filters are characterized by their two cutoff frequencies: the lower and upper limits of the frequency range they allow. By tuning these frequencies, engineers can design bandpass filters to meet specific needs, making them essential in devices like radios, cell phones, and musical instruments.