Modem

A modem (modulator-demodulator) connects a home or office to an internet service provider by converting digital data from computers into signals that travel over the provider's line (telephone, cable, fibre or mobile) and back again.

A modem gives one connection to the internet; a router then shares it among many devices and creates the local Wi-Fi network. Most broadband boxes from ISPs are modem and router in one. A fibre connection uses an ONT (Optical Network Terminal) in the modem's role.