They can be used to research your genealogy, to let others know what you think about the recent political races, or to find that special someone. Newsgroups are public discussions about a particular subject. Other users can then reply to the post to the the author know what they think. You will need a special news reader to read and post to a newsgroup.
Many email programs have the capability to read articles.
MS Outlook Express is one and Netscape Navigator and Communicator both come with the news reader Netscape News. News readers work similar to email clients. You should be able to catch on to a news reader, if you comfortable with the use of an email client. Now, pick a subject and find the appropriate newsgroup. Most news readers will also give you a list of available newsgroups.