Usenet is newsgroups or newsservers. It has been around for decades and was one of the earliest file sharing mechanism (not earlier than BBS over modem, but still old). The reason lots of torrent files are multi-rar archives is because of Usenet. I've been primarily using it for a couple years now. It can be a pain if you just use a news reader but several years back, .nzb files were developed, which the easiest description would be the .torrent file of Usenet. Grab the NZB file, load it up in a client that supports .nzb, and the client will download all the parts, combine them and extract. The caveat is typically you need to pay for Usenet access but the plus side is you're just downloading while most of the heat on file sharing is for uploading.
Indexing sites make it easier to find the .nzb file and also are a good source of feedback on whether or not the item is complete (often, some of the .rar files are missing). Right now, some of the good, popular ones are closing because the DMCA have submitted mass removal requests and rather then deal with it, the sites are just closing. Other sites will pop up but it's going to take a while so until then, I'm floundering.
