What is a newsgroup what are its main features and how does it differ from a chat room or news site?

What is a newsgroup what are its main features and how does it differ from a chat room or news site?
A newsgroup is basically a group e-mail service. Everyone on the list for that newsgroup receives any message which is posted. Since there is a special protocol for newsgroups within the TCP/IP suite of protocols which govern how things work on the Internet, programmers can very easily include newsgroups into software, most commonly email, such as Outlook Express. Bascially no one company created newsgroups and so there were no format wars or anything - it's worked pretty well from the start.Newsgroups were at their height of popularity in the late 1990s but have since declined, since people find it relatively difficult to set up a newsgroup within their software (or even know it's possible) whereas webpage based fora are more self explanatory. Since newsgroups were around during the massive escalation in spam in the late 1990's, they also got hit a lot by spammers and were associated with spam.Unlike a chat room, messages are not instaneous, and the viewer sees the subject line before deciding to read the rest.