Your Usenet access software
The Usenet and therefore also the newsgroups are accessed with a newsreader (also called a client). This is similar in its usage to the well-known Internet browsers (e.g. Mozilla Firefox or Internet Explorer) and therefore ensures simple navigation through the Usenet.
There are, of course, substantial differences between how the individual newsreaders work. Before you opt for a specific newsreader, you should for instance check which operating system it is suitable for. The languages on offer may also be relevant for your choice. Some Usenet providers offer their own software, while UseNeXT gives you a free choice.