Tell people about IRC today and they don't believe you
It's one of the early instant messaging systems, dating back to the late 80s. Until widespread availability of broadband in the UK, it suffered because of the costs of dial-up connections (much cheaper to send an email / use an 'offline reader' on a message board) and by the time it became 'free' to chat, other systems had used more or less dubious ways to get the attention and user numbers.
But it lives on. Various groups use IRC to hold online meetings, and I know some deaf friends who use it at home to talk to each other as they can type faster than they can sign!
it can be as simple as setting on up on say icq's network and linking to it
Gosh, I thought ICQ was dead and buried at a crossroads with a stake through its heart. Certainly, giving an ICQ 'number' on registration is one of the tests I use to detect spam registrations: only the spambots pretend to use ICQ now.
Personally, I think running your own chat room is much more trouble than it's worth, but it's not my decision