As you can see a cable modem is essentially an extremely powerful and in some ways complex radio transmitter and receiver. The technology works using radio signals transmitted to and from the cable modem which serves to translate these radio waves into the digital signals used on a computer system. Many cable operators use fibre optic networks which although at the moment are limited in the bandwidth they provide to customers they do have the backbone in place to potentially provide extremely high bandwidth Internet far exceeding that which xDSL technology is capable of achieving.

Also cable modems literally provide an 'always on' connection due to the fact that they themselves maintain a bridge to the Internet regardless of the status of your computer hardware. xDSL however actually uses the computer hardware to establish and maintain its Internet connection, therefore making the technology only online as long as your hardware is operational.