Cable TV is, as the name would suggest, this is TV through a cable, rather than an aerial or satellite. There are many benefits to this approach:

• A cable is easier to regulate than the atmosphere meaning many more channels can be squeezed into the available frequencies.
• The system can be adapted to allow high speed internet acess through Cable Modems. This is a good thing(tm)
• The use of set top boxes allows the signals to be encrypted, allowing the cable company to make huge sums of money by making you pay to watch certain events and/or channels.

For some reason Cable TV often comes bundled with cheap telephone deals. The formidable combination of cheap dialup, cable modems for the rich, and lots of cheap crap TV makes cable an ideal addition to any geek house.