style sheet vs piece of paper

style sheet and piece of paper both are nouns.

Word	Noun	Adjective	Verb	Adverb
style sheet	Yes	No	No	No
piece of paper	Yes	No	No	No

As nouns, piece of paper is a hypernym of style sheet; that is, piece of paper is a word with a broader meaning than style sheet:

style sheet: a sheet summarizing the editorial conventions to be followed in preparing text for publication
piece of paper: paper used for writing or printing

Other hypernyms of style sheet include sheet, sheet of paper.

style sheet (noun)	piece of paper (noun)
a sheet summarizing the editorial conventions to be followed in preparing text for publication	paper used for writing or printing