A UseNet client application that implements the NNTP Protocol and accompanying message format, much like a MailClient implements SMTP and accompanying message format and a WebBrowser implements HTTP and HTML, JavaScript, etc.
Integrated NewsReaders are included with the Netscape/Mozilla browsers and OutlookExpress (not MicrosoftOutlook); though using the latter might make you unpopular due to a large array of "perks" and annoyances that ignore established Netiquette.
A list of popular standalone NewsReaders for Linux includes:
With GUI:
For the console:
6 pages link to NewsReader:
Knode