Internet Relay Chat (IRC) is a no-frills text based chat system that was developed in the 1990s and requires client/server software to run.
It is mainly designed for group communication, which takes place in chatrooms and is overseen by operators. Operators are users that have privileged access and can disconnect or ban other users.
IRC is particularly popular among developers and other technically savvy individuals. It is simple and highly extensible, requires very little bandwidth,  and runs on low speeds. In addition, many IRC networks have IP cloaking and allow for connections from Tor nodes, VPNs, and proxies.