sidebar vs newspaper article

sidebar and newspaper article both are nouns.

Word	Noun	Adjective	Verb	Adverb
sidebar	Yes	No	No	No
newspaper article	Yes	No	No	No

As nouns, newspaper article is a hypernym of sidebar; that is, newspaper article is a word with a broader meaning than sidebar:

Other hypernyms of sidebar include news article, news story.

sidebar (noun)	newspaper article (noun)
(law) a courtroom conference between the lawyers and the judge that is held out of the jury's hearing	an article reporting news
a short news story presenting sidelights on a major story