Newsgroups are organized into category hierarchies of names and dots, which are read right to left. For example, alt.music.jazz means the jazz music topic in the alt (alternate) category. Categories are often designated with an asterisk to represent "all topics;" for example, talk.* means "talk.all," or the entire Talk category (see wild cards).

The Alt category is the most varied. The least moderated of newsgroups, Alt contains a huge number of topics, including x-rated material. The alt.binaries category is used to share non-text files, including software, images and videos. Following are the major categories. See newsgroup and Usenet.

   Category       Subjects

   alt            varied, x-rated
   alt.binaries   non-text (images, videos)

   biz            business (ads allowed)

   comp           computer (technical issues)

   misc           miscellaneous

   news           technical issues about Usenet

   rec            recreation (sports, travel, etc.)

   sci            science and medicine

   soc            social issues

   talk           debates, controversial topics