A newsgroup is an Internet-based discussion around an individual, entity, organization or topic. Newsgroups enable remotely connected users to share, discuss and learn about their topic of interest by exchanging text messages, images, videos and other forms of digital content.
Newsgroups are also referred to as usenet newsgroups.
Techopedia explains Newsgroup
Newsgroups were initially created in 1979 by some university students to exchange messages. Users can subscribe for free by submitting an email address, and the group generally consists of several topics/categories based around a main theme. The user/subscriber can post a message in a particular topic/category, which is either automatically visible in open newsgroups, or can only be viewed by approved members in moderated groups. All subscribers participating or following a particular topic/newsgroup will be notified of new messages and updates. Moreover, news/stories/topics in the newsgroup can be read through a downloadable news reader application.
Despite new technologies such as social media, newsgroups continue to thrive online.