DSL (digital subscriber line) is a method of Internet connection which gives the user the ability to connect to the Internet at an extremely high rate of speed over their regular phone lines by using special hardware attached to both the user and switch ends of line. DSL service attaches to your existing phone line, giving you a constant connection to the Internet without tying up the phone line.  It is similar to the service provided by some cable companies.  DSL comes in several forms: ADSL, HDSL, IDSL, R-ADSL, SDSL, and VDSL--DSL and offers users a choice of speeds.  Over any given link, the maximum DSL speed is determined by the distance between the customer site and the Central Office. 

DSL gives you great data transmission speed, but distance limitations and line quality conditions can reduce what will actually be achievable. This technology is still in the early stages .  These digital services will ultimately be used to deliver bandwidth-intensive applications like video on demand and distance learning. 

The advantage of DSL is that it is circuit oriented so that each connection is independent of all others, while cable networks are broadcast oriented, with each subscriber in an area receiving the same signals as all others in that area. Cable networks are inherently hierarchical in nature and thus require two paths, one for downstream and one for upstream. This requires either a second cable plant for upstream or a second frequency band allocated onto the existing system.

DSL, like cable, is not available in many areas. When it is available, installation can be fraught with difficulties. However, it is definitely worth the trouble. It is recommend that you purchase a firewall protection, such as a Linksys cable router. Their  model  BEFSR41 - EtherFast 4-Port Cable/DSL Router is it totally tamper-proof and easy to install, and you can network as many as four connections at the same time with no loss in bandwidth.