News is a public messaging system originating with USENET. In many ways it is similar to email, but instead of sending a message to an individual or to a small group a news message is broadcast more or less to the entire country or planet, depending on its topic.
To control just which portion of this cacophony you want to hear, news articles are classified into `newsgroups', each group representing a different topic. There are several thousand newsgroups, and more are being created all the time. Most people read only a few of these.