About IRCIRC stands for Internet Relay Chat and is a chat protocol that exists since the 90s/late 80s already,
which internet users been using for text chatting and sharing text for decades.
It is an alternative to the new Web 2.0 services (like Discord, Facebook, etc.),
that get more and more seen skeptical and untrustable by more and more people.
To connect to an IRC-Server, you can do that either via a Webchat, but the more usual way is
to do it via an IRC Client, which is an application you download.
Some IRC Clients for example are HexChat or mIRC for Windows
or irssi or Weechat for Linux in command line / HexChat or Konversation for Linux with GUI
or LimeChat for macOS.
All you gotta do is to download one of those IRC-Clients and to connect to one of our Servers.
If you want to learn more about IRC, one source for example is Wikipedia.