Usenet is a collection of internet message boards, discussion groups or newsgroups where the users can post messages and these posted messages are distributed via Usenet servers. 
Each board has a theme, and there are tens of thousands of usenets concerning every imaginable topic. Many of them cover professional subjects and societies and are rich sources of business information. 
- Usenet.org, What Is Usenet?
- American Marketing Association, AMA Dictionary.