A modem, short for modulator-demodulator, is a device primarily used for converting digital data from a computer into a format suitable for transmission over telephone lines, cable systems, or satellites, and vice versa. It enables Internet connectivity by facilitating the communication between your home network and your service provider. Modems are crucial in both residential and business settings, providing the backbone for accessing the internet, sending emails, streaming media, and conducting online meetings. They come with various specifications tailored to different needs, such as speed, compatibility, and type of service connection, ensuring users can find a match for their specific internet usage requirements.