Digital Subscriber Line - A residential and business based digital communication service in which the line onto the premises is not based on audio frequencies but instead carries digital signals directly. The effect of this is that data communications rates are possible which far exceed those achievable with Modems over a standard analog phone lines (POTS).

The high data rates associated with DSL make it an alternative to cable modems. The advantage DSL has over cable modems is that DSL is a direct "home run" connection to the network. So, available bandwidth will not degrade as neighbors begin using the service. The disadvantage is that DSL availability and speed depends on how far the user's premises are from the CO ("Central Office").

There are many different types or 'flavors' of Digital Subscriber Line services. To denote a specific type a letter is prefixed to the DSL acronym. For example, ADSL is Asymmetrical Digital Subscriber Line and SDSL is Symmetrical Digital Subscriber Line. When talking about DSL in general terms, it is usually referred to as simply "DSL" but is sometimes referred to as "xDSL" (where the 'x' denotes 'any' type letter).