What is Cable Modem?

Legal Definition
A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a hybrid fibre-coaxial (HFC) and radio frequency over glass (RFoG) infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. They are commonly deployed in Australia, Europe, Asia and the Americas.
-- Wikipedia
Legal Definition
A type of modem that connects a computer or local network to broadband Internet service through the same cable that supplies cable television service or the service connection made via a cable modem.