One way to think usenet/newsgroups is as a set of distributed peer-to-peer mailing lists.
You post a message to your (NNTP) server. Your server connects to other peer NNTP servers to transfer messages back and forth, so eventually your message will propagate throughout the usenet network. (40 years ago peering was through UUCP, etc, and done at night when phone calls were cheaper or only to other local numbers so it might take a week, now it doesn't take that long. See also, bang paths).
You post a message to your (NNTP) server. Your server connects to other peer NNTP servers to transfer messages back and forth, so eventually your message will propagate throughout the usenet network. (40 years ago peering was through UUCP, etc, and done at night when phone calls were cheaper or only to other local numbers so it might take a week, now it doesn't take that long. See also, bang paths).