Most users subscribe to a few newsgroups. Subscription is free and, once you locate the newsgroup you want, it usually involves one mouse click. Subscribing means that new message headings in that group are automatically downloaded when you start the newsreader. The messages in the newsgroups that start with melbpc are only visible to users who are using Melb PC as their ISP and cannot be read by users connected to other ISPs. You can read all messages and have the option of replying to an individual or to the group.
Some groups are very active and contain many hundreds or even thousands of messages.
Many of the newsgroups also contain programs or pictures. Look at the messages for one or two days before replying to anything to get the flavour of the discussion. This is called Lurking and is used as a means of learning before becoming a participant. When you post a letter, replies can come from all over the world. To illustrate the diversity and activity, I asked about the possible existence of a modification to the undercarriage for a particular make and model of a glider.