Digital Subscriber Line, abbreviated DSL, is a technology that brings high bandwidth information for businesses and homes over copper telephone lines. A digital subscriber line can deliver information hundreds of times faster than ordinary dial-up modems, thus reducing the time needed to download data files, web pages, animations and graphics. Generally, the download speed of DSL ranges from 128 kbps (kilobytes per second) to 6000 kbps. The change in the download speed depends on the DSL technology and service level implemented.

DSL is a broad term that consists of various variations - SDSL (Single-line Digital Subscriber Line), 1.5 Mbps; Asymmetric Digital Subscriber Line (ADSL), ranging up to 1.5 Mbps; Very high-data-rate Digital Subscriber Line (VDSL), ranging up to 2.3 Mbps; High-bit-rate Digital Subscriber Line (HDSL), 1.5 Mbps; and Rate Adaptive Digital Subscriber Line (RDSL), diverse speeds. A digital subscriber line facilitates separate channels for fax and voice. Hence, faxes and phone calls can be carried simultaneously with high-speed data across the line.

DSL technology was founded in 1988, when a group of engineers invented a method to transfer digital signals through the unexploited frequency spectrum available on the twisted pair of cables that run between a customer’s home and the telephone company's telephone exchange. Employing DSL technology in the telephone line provides digital communication without disturbing the voice services. DSL gained prominence in the late 1990s, when major cable television providers started marketing broadband Internet access. Today, Digital Subscriber Line is the main competition for cable modems in offering high speed Internet access to homes in North America and Europe. The latest standard ADSL2+ can provide more than 20 Mbit/s over about 1.2 miles.

Nowadays there are various types of DSL services tailor made for consumer needs. The main differences in these packages involve speed and how the direction data is delivered. For example, ADSL can provide higher data rates towards the subscriber than it does in the other direction. ADSL is perfect for home users who download information from the Internet. The symmetrical high-speed DSL is an ideal package for enterprise subscribers, who continuously send and receive data, or for those businesses that may need a two-way communication like videoconferencing.