Digital Subscriber Line (dsl) allows us to transmit voice,
data, video e.t.c simultanious on the same existing
telephone lines. in short DSL allows us to use both
telephone and internet simultaniously,

 service provider only provides the dsl modem as a part of
installation 
DSL is 20times faster than ordinary telephone and 10 times
faster than ISDN

DSL (Digital Subscriber Line) is a set of standards for 
broadband network connectivity over normal telephone lines