A modem (Modulator-Demodulator) is a networking device that enables your home or business network to connect to the internet. Its core function is to convert data between digital formats.It is used by computers and other local devices. Its role is to convert digital format to analog format (used for transmitting data over traditional communication lines like telephone wires or cables).
Modem was used in the early days of the Internet with Dial-up telephone lines.