Newsgroup

One of the earliest use of the Internet was to exchange messages between a group of like minded people. Even before the world wide web was created, there was a network called 'Usenet'.
This is still going strong today.
On Usenet, you can join thousands of newsgroups. There are at least 50,000 of them. You subscribe to the newsgroup and then begin to read and contribute to the 'threads' within each newsgroup.

A thread is a string of text based messages, from the first one that started the topic up to the latest one. The is where the first 'emoticons' such as :) (smiling face) came from and even before the mobile phone was invented, people were using text shortcuts such as IMHO (In My humble Opinion) or ROLF (Roll on Floor Laughing).

Some newsgroups are 'moderated' meaning someone is controlling what can and cannot be posted in that newsgroup.

The original main subject areas on Usenet are

comp.* — Discussion of computer-related topics
news.* — Discussion of Usenet itself
sci.* — Discussion of scientific subjects
rec.* — Discussion of recreational activities (e.g. games and hobbies)
soc.* — Socialising and discussion of social issues.
talk.* — Discussion of contentious issues such as religion and politics.
misc.* — Miscellaneous discussion—anything which doesn't fit in the other hierarchies.

You need a 'newsreader' application to use the newsgroups fully.