Usenet is a very old, worldwide discussion system on the internet. It started in 1980, before the web existed. It works like a huge set of public message boards, called newsgroups, each one about a single topic — cooking, cats, a certain computer language. You post a message, and computers called news servers pass copies of it around the world to each other, so there is no one company or one website that owns it. The name has "news" in it, but Usenet is not for reading the newspaper; "news" here means messages from other people. Group names look like addresses with dots, such as rec.food.recipes or comp.lang.c. Today most people talk about Usenet as history: it is where a lot of internet manners and words were born, including FAQ, spam and emoticons like :-). It still exists, and some people use it to share large files, but ordinary discussion has moved to the web. Write it with a capital U. It is a proper name, so it takes no "the" and no plural.