Broadband refers to a telecommunication signal in which a wide band of frequencies is available to transmit information. The signal is of greater bandwidth than usual signals, and has the capacity to deal with more traffic. It is able to deal with more information, because a wide band of frequencies is available, enabling information to be multiplexed and sent on many different frequencies or channels within the band concurrently. This means that more information can be transmitted in a given amount of time.

Bandwidth refers to the amount of data that can be transmitted over a given time period. Normally in data communications, a digital modem will transmit a datarate of 56 kilobits per second over a 4 kHz wide telephone line. When the same line is converted to a non loaded twisted pair wire, it becomes hundreds of kHz wide and can carry several megabits per second (Mbit/s). The wider or broader the bandwidth of a channel is, the greater the information carrying capacity is.

Regular telephone service uses less than one percent of the capacity of the telephone lines, leaving the remaining 99 percent of the line for high speed data use. Digital Subscriber Line (DSL) is a broadband circuit that is a family of technology that provides digital data over the wires of a local telephone network. DSL enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide.

There are currently at least six different types of DSL broadband circuits. They are Asymmetric Digital Subscriber Line (ADSL), Symmetric Digital Subscriber Line (SDSL), ISDN Digital Subscriber Line (IDSL), High-bit-rate Digital Subscriber Line (HDSL), Very high-bit-rate Digital Subscriber Line (VDSL), and Rate-Adaptive Digital Subscriber Line (RADSL). Each one has different technical ranges, capabilities, and limitations.

ADSL is the most common version of DSL broadband circuits. ADSL is called "asymmetric" because most of its two-way bandwidth is devoted to the downstream direction, sending data to the user. ADSL can generally be distributed over short distances from a central location. Basic ADSL broadband circuits deal with speeds of 8 Mbit/s downstream and up to 1.3 Mbit/s. ADSL2, extends the capability of ADSL to 12 Mbit/s downstream and up to 3.5 Mbit/s upstream. ADSL2+, which is a more advanced broadband circuit, goes up to 24 Mbit/s downstream and 3.3 Mbit/s.

SDSL is called ‘symmetric’ because its data rate is the same in both directions. It supports data only on a single line and does not support analog calls. Its data rates are between 1.5-2 Mbit/s. This broadband circuit cannot co-exist with a conventional voice service as it takes over the entire bandwidth.