Newsgroups/Usenet were around long before web browsers came into their own. If you wanted to use Usenet, you had to get Usenet software. But that history isn't particularly meaningful now, when Usenet and the browser-based internet have coexisted for years.
Years ago, a website called DejaVu (aka DejaNews) started archiving everything posted on Usenet and provided a search engine so people could find stuff. It was something Usenet users hadn't previously enjoyed. Now a posting doesn't just appear briefly and fade way. It becomes part of a searchable library. DejaVu eventually was bought by Google, so for many (including me) it has acquired the unofficial name "DejaGoo."
In addition to being able to search and read postings at DejaGoo, you can make postings of your own. So really it isn't strictly necessary anymore to use Usenet software such as FreeAgent, though I think it's a better tool.
Two other easy-to-get Usenet tools: You can use Outlook Express' built-in newsgroup reader, and of course Outlook Express is included with Windows 98 and later versions of Windows. The Netscape browser has a button to launch its own news reader.
I've provided controls right here that you can use to search on DejaGoo. But you should check out their site and read their stuff, too.
Search Google's newsgroup postings archive - Known by many as "DejaGoo," since Google bought it from DejaVu.
Google Groups (DejaGoo)
Main Newsgroup/Usenet Page
Main FAQ Page
Main Internet Primer Page
Bob Fahey's Home Page