Google Groups is just a way of viewing all the Usenet groups without having to have a newsreader and a news server provider. (and yes, it is free, but you do have to register your email with them to post on there) It's great, they have a massive archive of posts to search through, so you can find info on almost anything imaginable on there (and posts all the way back to the 80's when usenet started). when you search on google search engine, there's a tab at the top that you can click on to search the groups section.
- David