introductory article; advertisement
A written piece that introduces a product, service, person, or event, often in a magazine or newspaper. Can be a paid advertisement or a feature article.
An introductory article about the new product appeared in the magazine.
This introductory article was published as an advertisement.
広告 is a general advertisement, while 紹介記事 specifically refers to an article that introduces something, which may or may not be a paid ad.
記事 is a general article or news story, while 紹介記事 is specifically an introductory or promotional article.
Compound of 紹介 (introduction) and 記事 (article).