There are at least three news reading packages that operate inside Emacs. `rnews' comes with Emacs. GNUS and Gnews come separately. rnews will be replaced by GNUS in Emacs 19.
rnews works only with a local news spool directory. Both GNUS and Gnews handle reading news remotely via NNTP in addition to reading from a local news spool. GNUS supports reading mail stored in MH folders or articles saved by GNUS.
Gnews is styled after `rn' and seems to work like RMAIL. GNUS feels more like VM. People have complained that GNUS uses a lot of CPU time (it does). Some people have complained that Gnews is slower than GNUS.
For more information about GNUS, see section GNUS -- news reader within Emacs.
Gnews was written by Matthew P. Wiener <weemba@libra.wistar.upenn.edu>. The latest version seems to be 2.0, posted October 3, 1988. Matthew posted some fixes on October 26, 1988. Gnews does not appear to have been supported after this date. In particular, it has been reported that Gnews does not work with Emacs 18.57. There is a newsgroup for Gnews called gnu.emacs.gnews.