DSL stands for the following.
The digital subscriber line technology is the most common technology for Internet access in the UK. The advantage of DSL is that it works upon the copper line telephone network of the UK. The advantage of DSL, is that most locations in the UK can take advantage of the technology; unlike with a fibre optic network, which needs new cabling laying. Before DSL was implemented by Internet Service Providers in the UK, dialup and ISDN (a type of DSL) technologies were the most common ways to access the Internet. Dialup for domestic homes, whereas ISDN was primarily used by businesses. The problem with a dialup connection - alongside its slow upload / download speed - is that the telephone line could not be used when a connection to the Internet was established.
The advantage of implementing a digital subscriber line is that it can be used simultaneously alongside the telephone line. The only requirement is the use of a DSL filter: otherwise DSL will monopolise the telephone line, just like with a dialup connection. As of 2010, DSL supports a download speed of between 256 Kb/s to 24 Mbit/s. The problem with the UK's copper line telephone network: is that a speed of 24 Mbit/s is rarely achievable. In fact, the UK Government was/is attempting to meet a goal of an average download speed of just 2 Mbit/s by 2015.