A modem, which stands for Modulator-Demodulator, is a networking hardware device. Its primary function is to convert digital signals generated by a computer or other digital device into analog signals that can be transmitted over traditional analog communication channels like telephone lines or coaxial cables (modulation). Conversely, it receives incoming analog signals from the communication line and converts them back into digital signals that the computer can understand (demodulation). This process allows digital devices to communicate over analog infrastructure.