DSL vs subscriber line

DSL and subscriber line both are nouns.

Word	Noun	Adjective	Verb	Adverb
DSL	Yes	No	No	No
subscriber line	Yes	No	No	No

As nouns, subscriber line is a hypernym of DSL; that is, subscriber line is a word with a broader meaning than DSL:

DSL: a generic name for digital lines that are provided by telephone companies to their local subscribers and that carry data at high speeds
subscriber line: a telephone connection

Other hypernyms of DSL include line, phone line, telephone circuit, telephone line.

DSL (noun)	subscriber line (noun)
a generic name for digital lines that are provided by telephone companies to their local subscribers and that carry data at high speeds	a telephone connection