INN (InterNetNews), originally written by Rich Salz, is an extremely
flexible and configurable Usenet / netnews news server.  For a complete
description of the protocols behind Usenet and netnews, see RFC 1036 and
RFC 977 (or their replacements).  In brief, netnews is a set of
protocols for exchanging messages between a decentralized network of
news servers.  News articles are organized into newsgroups, which are
themselves organized into hierarchies.  Each individual news server
stores locally all articles it has received for a given newsgroup,
making access to stored articles extremely fast.  Netnews does not
require any central server; instead, each news server passes along
articles it receives to all of the news servers it peers with, those
servers pass the articles along to their peers, and so on, resulting in
"flood fill" propagation of news articles.

INN supports accepting articles via either NNTP connections or via UUCP.
innd, the heart of INN, handles NNTP feeding connections directly; UUCP
newsfeeds use rnews (included in INN) to hand articles off to innd. 
Other parts of INN handle feeding articles out to other news servers,
most commonly innfeed (for real-time outgoing feeds) or nntpsend and
innxmit (used to send batches of news created by innd to a remote site
via TCP/IP).  INN can also handle outgoing UUCP feeds.
