Broadband is a high-speed way of connecting to the internet.
It is typically 10 times faster than so-called dial-up net services that use a modem and standard telephone line.
Broadband can be accessed via the phone line (known as Asymmetric Digital Subscriber Line) or by cable, wireless or satellite.
In the UK cable can be accessed only in areas where either Telewest or NTL supplies it. Wireless or satellite tend to be available in more remote spots.
ADSL uses technology which allows data to be carried alongside normal calls on standard telephone lines.
Cable broadband is carried via optic fibres, which also provide digital TV and telephone services.
In each case, the data is carried along lines or cables that have more capacity than conventional ones.
Access speed is measured in bits per second: 512 kilobits (512k) is 10 times the speed of dial-up; 1 megabit (1mb) is 20 times faster.
The two big advantages of broadband over dial-up are that it frees up the telephone line for voice calls and can be left on permanently.
It still requires a modem, which is paid for when you sign up.
Broadband finally became regarded as a "mass market" product in the UK in 2004 when prices fell below £20 a month for the 512k version.
And the gap between charges for broadband and dial-up services is continuing to narrow.
Broadband allows you to browse the internet much faster as the pages download more quickly.
It can be used for downloading files, such as music or films, although some providers restrict the amount of downloading that can be made.
Broadband can be used to view video clips, take part in video conferencing and online gaming.
Increasingly, people are using it to make telephone calls over the internet.
BT owns most of the UK's domestic phone lines, known as the local loop, leaving the range of ADSL broadband services largely in its control.
Initially the cost of accessing BT's network proved prohibitively expensive for most potential rivals.
Recent price falls mean they can now provide extra services, which previously had been at the whim of BT.
This could lead to super-fast broadband and other services, such as cheap net phone calls and video on demand.
Broadband is set to get even faster, with video-quality bandwidth expected by 2010.
Services will increasingly come bundled with telephony and TV. High-definition television over broadband networks is likely.
World leaders are Japan and South Korea, where around 70% of households have a broadband connection of more than 20mb.
Future services will include video-on-demand and time-shifted TV.