A newsgroup name consists of the hierarchical topics and subtopics separated by periods.
This example describes a newsgroup that is specifically interested in medical discussions
of lyme disease. 
What is Network News?
Each newsgroup category can be compared to an organizational chart. For
example, in the science (sci) category, there are many subtopics (some of which are shown
below), which in turn may have subtopics.
A newsgroup name consists of the hierarchical topics and subtopics separated by periods.
This example describes a newsgroup that is specifically interested in medical discussions
of lyme disease.