At that time, the newsgroups were categorized into three hierarchies: "fa." for groups for ARPANET, "mod." for moderated discussions, and "net." for unmoderated groups. Names of the groups were said to be rather haphazard. (see The Great Renaming FAQ.)
The backbone providers, or the backbone cabal, were instrumental in this reorganization of Usenet since they had a great influence on supporting a new newsgrop. Some suggest that members of cabal had interests in bundling certain newsgroups into talk hierarchy, in order not to be objected by their supervisors. 
A more detailed account of reasons behind the Renaming can also be seen in a email message by Gene Spaford at net.news and net.news.group.
These newsgroups were categorized into a series of hierarchies, to make it easier for newsgroups to be created and distributed. These hierarchies were initially set as:
Several other popular hierarchies remained on Usenet as well, such as the k12.* hierarchy (which covered topics especially relating to education, schools, and colleges).
An additional hierarchy, the alt hierarchy, was also created shortly after the Renaming. The term "alt" was originally meant as a humorous acronym for "anarchists, lunatics, and terrorists," though it became widely known as "alternative." The alt.* hierarchy was meant to be completely free from outside control, and it was not subject to the regulations of the Big Seven.
In the mid 1990s, when the Usenet traffic grew significantly, one more hierarchy "humanities" was introduced, and with the seven hierarchies created by the Renaming, conprises today's so-called "Big Eight".
See also: Gene Spafford, Rick Adams