What exactly is Usenet?

I've heard about it several times in the past year, primarily that it's going to outclass Bittorrent eventually.  But it seems I'd need an entirely new ISP or something to use it?  What exactly is it, and how does one access it?  If it makes any difference, I'm using Optimum Online.

>>1
For using Usenet to download various oddities, you should check you should check out NewsBin [ http://www.newsbin.com/ ]. Optimum Online has their server at news.optonline.net . I can also tell you that they do not let you download at the maximum speed they can, capping you off at about 120 KiB/s.